The DOI matches its Crossref record; 263 of the 263 references it cites were found in a registry or an index; none of the 200 sources its claims cite is checked for support yet.
Exoplanet Biosignatures: A Framework for Their Assessment
Open accessAbstract
Finding life on exoplanets from telescopic observations is an ultimate goal of exoplanet science. Life produces gases and other substances, such as pigments, which can have distinct spectral or photometric signatures. Whether or not life is found with future data must be expressed with probabilities, requiring a framework of biosignature assessment. We present a framework in which we advocate using biogeochemical "Exo-Earth System" models to simulate potential biosignatures in spectra or photometry. Given actual observations, simulations are used to find the Bayesian likelihoods of those data occurring for scenarios with and without life. The latter includes "false positives" wherein abiotic sources mimic biosignatures. Prior knowledge of factors influencing planetary inhabitation, including previous observations, is combined with the likelihoods to give the Bayesian posterior probability of life existing on a given exoplanet. Four components of observation and analysis are necessary. (1) Characterization of stellar (e.g., age and spectrum) and exoplanetary system properties, including "external" exoplanet parameters (e.g., mass and radius), to determine an exoplanet's suitability for life. (2) Characterization of "internal" exoplanet parameters (e.g., climate) to evaluate habitability. (3) Assessment of potential biosignatures within the environmental context (components 1-2), including corroborating evidence. (4) Exclusion of false positives. We propose that resulting posterior Bayesian probabilities of life's existence map to five confidence levels, ranging from "very likely" (90-100%) to "very unlikely" (<10%) inhabited. Key Words: Bayesian statistics-Biosignatures-Drake equation-Exoplanets-Habitability-Planetary science. Astrobiology 18, 709-738.
Overview
AI snapshot
Written from the paper’s full text.
TL;DR
The paper proposes a Bayesian framework for assessing exoplanet biosignatures, combining prior knowledge about habitability with likelihoods of spectral or photometric data under scenarios with and without life. It outlines four observational/analytical components and maps posterior probabilities of life to five qualitative confidence levels.
Key findings
- The framework’s central quantity is \(P(\text{life} \mid \text{data, context})\), calculated from priors \(P(\text{life} \mid C)\) and likelihoods \(P(D \mid C, \text{life})\) and \(P(D \mid C, \text{no life})\), where the latter includes abiotic false positives.
- In an illustrative example with prior \(P(\text{life} \mid C)=0.5\), \(P(D \mid C,\text{life})=0.80\), and \(P(D \mid C,\text{no life})=0.25\), the posterior is \(0.76 \equiv 76\%\).
- The authors propose five confidence levels for life detection: Level 1 “very likely inhabited” 90–100%, Level 2 “likely inhabited” 66–100%, Level 3 “about as likely as not inhabited” 33–66%, Level 4 “likely uninhabited” 0–33%, and Level 5 “very likely uninhabited” 0–10%.
- The four required components are: (1) stellar and external exoplanetary system properties, (2) internal exoplanet atmosphere/climate/surface properties, (3) search for potential biosignatures in data, and (4) exclusion of false positives.
Methods
- Conceptual and statistical framework paper, not an empirical exoplanet observation study; it develops Bayes’ theorem for biosignature assessment and discusses required observations and models.
- It advocates using biogeochemical “Exo-Earth System” models to simulate potential biosignatures in spectra or photometry and to estimate Bayesian likelihoods with and without life.
- It reviews desirable stellar, planetary, atmospheric, and surface parameters; candidate gaseous and surface biosignatures; and false-positive scenarios, with illustrative examples rather than new data analysis.
Limitations
- The paper states that current knowledge of priors such as \(P(\text{life} \mid \text{Earth-like})\) is highly uncertain, ranging from life being very common to very rare, and that extraterrestrial life has not yet been detected.
- It states that many false-positive scenarios and surface biosignature assessments remain unresolved; for example, “a quantitative framework for evaluating surface biosignatures remains unclear,” and the confidence-level examples are “purely illustrative.”
- Evident from the text: the framework is not tested on real exoplanet data, relies on future models and observations, and its posterior probabilities cannot yet be quantified for specific exoplanets without detailed calculations.
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Claims the paper makes
116 Not checked yet · 104 Own interpretation · 46 No basis given
In the paper
“Consequently, the distinction between inhabitation and habitability can become blurred (Goldblatt, 2016).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Goldblatt, 2016
plaincorrelational- Asserted: passes — The authors put it forward as true.
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In the paper
“The probability P(life | context) shown in Figure 1 refers to a particular exoplanet under observation but is related to the term fl in the Drake equation that applies to an ensemble of exoplanets (Des Marais, 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Des Marais, 2015
plaincorrelational- Asserted: passes — The authors put it forward as true.
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- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
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None of the sources cited for this claim have been checked yet.
In the paper
“Regarding habitability, the ubiquitous concept of the HZ is built upon the assumption that P(life | C) is higher where the context is an exoplanet orbiting within a certain range of star–planet distances (Kasting et al., 1993; Kasting, 1997; Kopparapu et al., 2013).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Kasting et al., 1993
- Not checked yetcites Kasting, 1997
- Not checked yetcites Kopparapu et al., 2013
plaincorrelational- Asserted: passes — The authors put it forward as true.
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In the paper
“On Earth, the biosphere modulates all the major atmospheric gases, such as O2 and N2, and most trace gases with the exception of noble gases (e.g., Catling and Kasting, 2017).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Catling and Kasting, 2017
plaindirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: passes — The paper’s conclusions depend on it.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This Bayesian insight cautions us that exoplanet data might be overoptimistically interpreted to indicate the presence of life, if life is actually very rare in the galaxy.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
hedgedconditional- Asserted: passes — The authors put it forward as true.
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None of the sources cited for this claim have been checked yet.
In the paper
“The conventional limits of the HZ are calculated with an Earth-like climate assumed to arise from a CO2–H2O-rich atmosphere.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Kasting et al., 1993
- Not checked yetcites Kasting, 1997
- Not checked yetcites Kopparapu et al., 2013
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“The possibility of false positives—when a planet without life produces a spectral or photometric feature that mimics a biosignature—is a lesson learned from consideration of oxygen and ozone (O3) as biosignatures (Meadows et al., 2018, in this issue).”
- Also stated in: § Abstract · plain
“The latter includes “false positives” wherein abiotic sources mimic biosignatures.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 1. Introduction
What the sources say
- Not checked yetcites Meadows et al., 2018
plaindirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: passes — The paper’s conclusions depend on it.
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- Also stated in: § Abstract · plain
In the paper
“Furthermore, some environmental contextual parameters on the planet may be modulated by life, for example, the bulk atmospheric composition and resulting climate.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Catling and Kasting, 2017
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This posterior probability would be low and dominated by the small prior, P(life | C), unless the probability of a false positive is very small.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- The authors state this as an assumption: For the framework, the presence of life is treated as a binary variable: a remotely detectable surface biosphere is either present or absent.
In the paper
“the probabilities P(M-stars), P(K-stars), etc. are the observed occurrence probabilities in our galaxy of main sequence stellar types, which sum to unity: 0.76 for M-stars, 0.12 for K-stars, 0.076 for G-stars, 0.03 for F-stars, 0.006 for A-stars, 0.0013 for B-stars, and ∼10−5 for O-stars (Ledrew, 2001).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Ledrew, 2001
plain- Asserted: passes — The authors put it forward as true.
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- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“it will be less than fl in the Drake equation, which refers to life arising on habitable planets at any time.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, P(life | Earth-like) is not a totally unknown probability where, following Laplace, we would have to assume it is equally likely to have any value from 0 to 1.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plainSingle case- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In the former case, the “base rate” of uninhabited C-type exoplanets, which is reflected by the small prior P(life | C), would far outweigh the number of inhabited C-type exoplanets.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- The authors state this as an assumption: For the framework, the presence of life is treated as a binary variable: a remotely detectable surface biosphere is either present or absent.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus, the correct prior for assessing biosignatures is P(life | C), which captures the intertwining of life and environment rather than P(life).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Knowledge of an exoplanet's obliquity (axial tilt) would give a more complete picture of habitability through the effect of seasonality on heat transport around the planet.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
hedgeddirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Consequently, knowledge of stellar activity is desirable since it may affect our prior, P(life | C).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
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None of the sources cited for this claim have been checked yet.
In the paper
“The spectral type and effective temperature of a star are essential parameters for estimating the stellar flux on an exoplanet, which is a key parameter for the planetary climate and habitability”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
What the sources say
- Not checked yetcites Pierrehumbert, 2010
- Not checked yetcites Kopparapu et al., 2013
- Not checked yetcites Catling and Kasting, 2017
plaindirect- Asserted: passes — The authors put it forward as true.
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The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Knowing the age of the star and current luminosity provides context for assessing the potential evolution of an exoplanet's atmosphere and possible life.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
plaincorrelational- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The orbital eccentricity is also essential for a model of the possible atmospheric evolutionary history, the seasonal climatic variations on an exoplanet, and potential planet–planet dynamical interactions.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
plaindirect- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The gravitational acceleration, g, of an exoplanet is necessary for understanding a variety of atmospheric parameters, including the scale height and lapse rate”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
plaindirect- Asserted: passes — The authors put it forward as true.
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None of the sources cited for this claim have been checked yet.
In the paper
“The SED is also necessary to run photochemical models that disentangle possible gaseous biosignatures from abiotic false positives, as explored for O2 and O3”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
What the sources say
- Not checked yetcites Domagal-Goldman et al., 2014
- Not checked yetcites Tian et al., 2014
- Not checked yetcites Gao et al., 2015
plaindirect- Asserted: passes — The authors put it forward as true.
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In the paper
“But many biomolecules rapidly degrade >150°C (White, 1984; Somero, 1995) irrespective of the influence of high pressure, which may be stabilizing or destabilizing (Lang, 1986; Bains et al., 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites White, 1984
- Not checked yetcites Somero, 1995
- Not checked yetcites Lang, 1986
plaindirect- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“These likelihoods do not necessarily sum to unity, as illustrated in the previous illustrative example.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plain- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Second, a very young planet is unlikely to have developed life that had time to evolve the complex biochemistry necessary to substantially alter its environment, and hence produce a detectable biosignature.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
hedgedconditional- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The SED also directly affects the HZ, which is a key part of the context-dependent prior”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
plaindirect- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In the future, if data from an exoplanet become more and more difficult to explain by abiotic explanations”
- Also stated in: § 2. A Bayesian Framework for Biosignature Assessment and Life Detection · plain
“then the second term in the denominator of Eq. 7 will become negligible.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plaindirect- Asserted: passes — The authors put it forward as true.
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- Also stated in: § 2. A Bayesian Framework for Biosignature Assessment and Life Detection · plain
None of the sources cited for this claim have been checked yet.
In the paper
“The spectral energy distribution (SED) is needed to understand atmospheric chemistry because it affects the reactions of key molecules of interest on a habitable exoplanet, such as CO2, CH4, O2, and H2O”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
What the sources say
- Not checked yetcites Segura et al., 2003
- Not checked yetcites Grenfell et al., 2007
- Not checked yetcites Rugheimer et al., 2013
plaindirect- Asserted: passes — The authors put it forward as true.
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In the paper
“The panchromatic spectrum, including the UV flux, provides an essential input for models of the atmospheric chemistry, climate, and atmospheric escape of exoplanets”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
What the sources say
- Not checked yetcites Linsky and Güdel, 2015
plaindirect- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Hence, the probability of life on an exoplanet with data suggestive of biosignatures will converge to 1”
- Also stated in: § 2. A Bayesian Framework for Biosignature Assessment and Life Detection · plain
“regardless of the exact choice of the “prior” P(life | C) and irrespective of the exact computed likelihood”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plaindirect- Asserted: passes — The authors put it forward as true.
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- Also stated in: § 2. A Bayesian Framework for Biosignature Assessment and Life Detection · plain
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A planet inside a HZ is not necessarily habitable.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plain- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus, a conservative upper limit on Tsurfe for a habitable planet is Tsurfe < 425 K.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plain- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If proposed false positive scenarios prove to be less realistic than some hypothesize, detecting life from Earth-like exoplanet biosignatures becomes mathematically more favorable.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plaindirect- Asserted: passes — The authors put it forward as true.
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A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“if future data from exoplanets become increasingly difficult to explain without invoking the presence of life, it turns out that the exact value for the assumed “prior” does not matter.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plain- Asserted: passes — The authors put it forward as true.
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- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
- The authors state this as an assumption: In the absence of other information, a prior of P(life | Earth-like) = 0.5 is a practical starting point for an Earth-like planet in the HZ of a Sun-like star.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A surface temperature 647 K—water's critical temperature at which water can only exist as vapor—is the likely firm physical limit for habitability.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedged- Asserted: passes — The authors put it forward as true.
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In the paper
“In the solar system, the surface of Venus is obscured because visible and IR radiation is scattered or absorbed and emitted from far above the surface (Titov et al., 2013).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Titov et al., 2013
plaindirectSingle case- Asserted: passes — The authors put it forward as true.
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- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
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None of the sources cited for this claim have been checked yet.
In the paper
“However, thick hazes, clouds, or a highly absorptive and scattering atmosphere can prohibit a direct view of a planet's surface across a very broad range of wavelengths.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Finally, a third way to infer an ocean is from a very attenuated light curve of thermal emission from an Earth-like planet with seasonality, which may indicate a high thermal inertia that would require an ocean (Gaidos and Williams, 2004).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Gaidos and Williams, 2004
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“but we note that substantial liquid water oceans have large thermal inertia and will likely moderate the effect of eccentricity on habitability even if oceans are periodically ice covered (Kane and Gelino, 2012).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Kane and Gelino, 2012
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“In principle, detection of a glint spot of specular reflection indicates the presence of a large body of liquid water (Sagan et al., 1993; Williams and Gaidos, 2008; Robinson et al., 2010).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Sagan et al., 1993
- Not checked yetcites Williams and Gaidos, 2008
- Not checked yetcites Robinson et al., 2010
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“The calculated extent of the conventional HZ relies upon the idea that the carbonate–silicate thermostat [originally proposed by Walker et al. (1981) for the Earth] will apply to other HZ rocky worlds.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Walker et al., 1981
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Consequently, the fraction of the light that is polarized could be used to infer whether an exoplanet has a liquid water ocean (Stam, 2008; Williams and Gaidos, 2008; Zugger et al., 2010).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Stam, 2008
- Not checked yetcites Williams and Gaidos, 2008
- Not checked yetcites Zugger et al., 2010
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In addition to Bond albedo and stellar flux, knowledge of the concentrations of greenhouse gases, such as those listed in Table 3, is also needed to calculate ΔTgreenhouse in Eq. 13 and thus surface temperature.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“The presence of Si-O on airless rocky exoplanets would produce features in thermal IR emission bands (Hu et al., 2012a), but these would be obscured by a thick atmosphere at temperatures typical of habitability.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Hu et al., 2012a
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Unpolarized light incident on an ocean surface will be reflected with some degree of polarization, which peaks at the Brewster angle.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“in fact, planets with atmospheres in our solar system have a wide range of Bond albedos from 0.76 on Venus (Moroz et al., 1985) to 0.25 on Mars (Pleskot and Miner, 1981).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Moroz et al., 1985
- Not checked yetcites Pleskot and Miner, 1981
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Bond albedo is a more important parameter for Earth-like exoplanets than for giant planets because of surface temperature being key for habitability.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The presence of abundant CO would also tend to argue against a liquid water surface because the photochemical sink of CO is the OH radical, which atmospheric chemistry should produce in relative abundance from near-UV photolysis if water vapor evaporates from an ocean.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Liquid or frozen water on a surface has spectral features that are broadened and shifted to different wavelengths compared with water vapor.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Fletcher, 1970
- Not checked yetcites Warren and Brandt, 2008
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“In addition, on a habitable world, the presence of CO2 indicates a possible substrate for biological carbon fixation (e.g., Raven et al., 2012).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Raven et al., 2012
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“With sufficient spectral resolution, strong CO2 absorption bands can be inverted to retrieve the vertical temperature profile above the surface of a planet or above a cloud surface (e.g., Twomey, 1996; Rodgers, 2000).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Twomey, 1996
- Not checked yetcites Rodgers, 2000
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“The structure of strong absorption bands of a well-mixed gas is required to retrieve atmospheric structure.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“In transmission spectra, Rayleigh scattering can set a lower limit on atmospheric pressure, given that transmission does not probe down to the planetary surface or below clouds (Lecavalier Etangs et al., 2008; Benneke and Seager, 2012).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Lecavalier Etangs et al., 2008
- Not checked yetcites Benneke and Seager, 2012
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Also, substantial cloud cover can mute absorption features in reflectance spectra (Kaltenegger et al., 2007; Rugheimer et al., 2013).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Kaltenegger et al., 2007
- Not checked yetcites Rugheimer et al., 2013
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“But detection of CO2 is also valuable because it should be a well-mixed atmospheric constituent that allows retrieval of atmospheric temperature structure from spectral data, which is necessary to obtain the abundances of other gases, including possible biosignature gases (see section 3.3).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If the planet's surface temperature is suitable, a large amount of water vapor could only be explained by evaporation from a large body of liquid water on a planet's surface rather than the cool top of a steam atmosphere.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“On Earth, CO is a gas that is readily consumed by microbes in the presence of water, serving both as a metabolic substrate and carbon source (Ragsdale, 2004), and it was probably readily consumed from the primitive atmosphere once life developed (Kasting, 2014).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Ragsdale, 2004
- Not checked yetcites Kasting, 2014
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“For N2 partial pressures >0.5 bar, collisional pairs of nitrogen, that is, N2–N2, produce a detectable absorption signal in transit transmission or reflectance spectra at 4.15 μm in the wings of the strong 4.3 μm CO2 absorption band (Schwieterman et al., 2015b) (Table 3).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Schwieterman et al., 2015b
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Given that CO is easily oxidized or reduced, it is plausible that microbe-like life elsewhere would remove CO and suppress its atmospheric abundance.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Clouds and hazes tend to diminish the sensitivity of transit spectra to the deep atmosphere (Knutson et al., 2014; Kreidberg et al., 2014; Robinson et al., 2014; Robinson, 2018).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Knutson et al., 2014
- Not checked yetcites Kreidberg et al., 2014
- Not checked yetcites Robinson et al., 2014
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Reducing atmospheres at low or moderate temperatures tend to contain organic hazes, as observed on Titan and the giant planets of the solar system.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
In the paper
“indeed, geochemical evidence suggests its presence by 3.5 billion years ago (Ueno et al., 2006).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Ueno et al., 2006
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“The Earth began with a chemically reducing atmosphere that became increasingly oxidized and oxidizing over its history (reviewed by Catling and Kasting, 2017).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Catling and Kasting, 2017
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“In transit transmission spectroscopy, a long pathlength means that a haze with only modest vertical optical depth can cause substantial broadband opacity (Fortney, 2005).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Fortney, 2005
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Cloudy planets, like those in the solar system, tend to have relatively high geometric albedos (Demory et al., 2013; Marley et al., 2013).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Demory et al., 2013
- Not checked yetcites Marley et al., 2013
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Based on the detectability of Earth-based life, it is expected that the most detectable biogenic substances in exoplanetary spectra will be gases.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Precisely designed sensor bands avoid the range 700–760 nm where the red edge is steep, and target adjacent red and NIR bands to measure the strongest contrast in reflectance.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“This particular biosignature also exhibits strong temporal variability due to seasonal changes in vegetation distribution and density, adding further observational potential (Schwieterman et al., 2015a).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Schwieterman et al., 2015a
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“But hydrogen bonding constrains bending, so the bending “spring constant” becomes stiffer and bending vibrations are shifted to shorter wavelength: from 6.27 μm in vapor to 6.10 μm in ice (Warren and Brandt, 2008).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Warren and Brandt, 2008
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Similarly, ammonia has difficulty accumulating to detectable concentrations on planets with Earth-like amounts of radiation from their host stars, even in relatively reducing atmospheres (Sagan and Chyba, 1997).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Sagan and Chyba, 1997
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Other trace gases could potentially indicate volcanism, such as SO2, H2S, and HCl (Kaltenegger et al., 2010).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Kaltenegger et al., 2010
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In both oxic and weakly reducing atmospheres, some SO2 and H2S can be oxidized to a sulfate aerosol haze.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plainconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Consequently, photosynthetic O2 (from oxidation of water to obtain electrons and hydrogen to reduce CO2 to organic carbon) or N2O (from reducing oxides of nitrogen with organic carbon) are ways that microbe-like entities anywhere could use energy for carbon fixation or other biological processes.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Techniques for detecting the gaseous components of an atmosphere and the structure of the atmosphere have been demonstrated on larger, uninhabitable planets (Benneke and Seager, 2012; Barstow et al., 2013; Lee et al., 2013; Line and Yung, 2013; Line et al., 2013; Line et al., 2014; Waldmann et al., 2015; Feng et al., 2016; Rocchetto et al., 2016).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Benneke and Seager, 2012
- Not checked yetcites Barstow et al., 2013
- Not checked yetcites Lee et al., 2013
boosted- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“For example, around a Sun-like star, photochemical destruction prevents the build up of remotely detectable levels of many organic sulfur gases for biospheric fluxes into the atmosphere that are comparable with those of the modern Earth (Domagal-Goldman et al., 2011).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Domagal-Goldman et al., 2011
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“As described by Schwieterman et al. (2018, in this issue), on Earth, the vegetation “red edge” is recognized as a globally detectable signature of life, which is a sharp increase in reflectance at ∼0.67–0.76 μm (Sagan et al., 1993; Seager et al., 2005).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Schwieterman et al., 2018
- Not checked yetcites Sagan et al., 1993
- Not checked yetcites Seager et al., 2005
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“At longer wavelengths, where thermal emission by the surface and atmosphere dominates over reflected light, the shape of strong absorption bands of vertically well-mixed gases (such as CO2 for an Earth-like world) makes it possible to determine the temperature structure and retrieve the abundances of gases from altitude- and temperature-dependent IR emission contributions (weighting functions), as”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Consequently, transient increases in NIR extinction in transmission spectroscopy due to aerosol loading could be a signature of pulses of explosive volcanism on an exoplanet (Misra et al., 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Misra et al., 2015
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In addition to gaseous atmospheric biosignatures, some organisms produce pigments with characteristic spectral reflectance features (Table 5).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“More recent estimates suggest that lower noise instruments can detect this band with spectral resolutions ∼150 (Brandt and Spiegel, 2014).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Brandt and Spiegel, 2014
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Stretching vibrations are shifted to longer wavelengths in the condensed phase: from 2.66 and 2.73 μm in water vapor to 2.87 and 3.05 μm in liquid, to 3.08 and 3.18 μm in ice (Fletcher, 1970, his Table 2.1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Fletcher, 1970
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Such spectral signatures could increase the confidence of the discovery of life on exoplanets.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If a biosphere modulates the composition of a planetary atmosphere, then it will tend to remove gases that are easy to metabolize.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For example, the detection of O2 would be corroborated by the detection of O3 in the atmosphere because O3 is a photochemical product of O2, if the star produces adequate near-UV flux.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Such pairs of detections can also be used to help constrain gas concentrations—for example, the O3 amount depends on the O2 concentration, although nonlinearly (Kasting et al., 1985).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Kasting et al., 1985
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“This disequilibrium is biogenic because current levels of both atmospheric N2 and O2 would not persist in the absence of biogenic fluxes of both gases (e.g., Som et al., 2016; Stüeken et al., 2016).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Som et al., 2016
- Not checked yetcites Stüeken et al., 2016
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In a reducing atmosphere analogous to that of the Archean Earth on an inhabited planet, we would not expect H2 to attain a high abundance in the presence of CO2 because these two substances can be readily used as metabolic reactants to produce CH4 through the methanogenesis pathway, CO2 + 4H2 → CH4 + 2H2O.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Arnold (2008) investigated the red edge in the Earthshine defining an index VRE = (RNIR − RRED)/RRED, which provided a simple measure of the NIR reflectance bump in the absence of atmospheric correction (VRE is not a standard index in vegetation remote sensing and Arnold used the reflectance in a narrow NIR spectral range [740–800 nm] for RNIR and reflectance in a narrow red band [600–670 nm] for”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Arnold (2008)
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Finally, if there is enough information about the atmospheric composition and planetary environment, it may be possible to quantify atmospheric chemical disequilibrium.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Besides the red edge, life produces a great diversity of pigments from phototrophic light-driven transmembrane proton translocation to photoreactive, phototactic, photoprotective, and photorepair systems, respiration components, and photosynthetic reaction centers (Schwieterman et al., 2015a).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Schwieterman et al., 2015a
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“On Earth, many of these biological surface features are only detectable in local remote sensing data, and whether any of these features could dominate on a global scale on an exoplanet remains an open question.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
In the paper
“Often, many of these pigments, such as carotenoids in halophilic Archaea, may be expressed in response to environmental chemistry, such as oxygen concentration or pH, in addition to light intensities (Slonczewski et al., 2010).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Slonczewski et al., 2010
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The presence of a biosignature gas should also be accompanied by its expected photochemical products.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The absorption maxima varies from UV to NIR (0.1–2.5 μm).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus, if the concentration ratio of CO2:CH4:H2 consists of sharply declining numbers, it would be consistent with the presence of biosphere in which methanogenesis is converting CO2 and H2 into CH4.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“For space-based telescopes such as the Terrestrial Planet Finder/Darwin concepts (Beichman et al., 2007; Defrère et al., 2017), the exposure times would be ∼100 h to reach a sufficient spectral precision (<3%) with a spectral resolution (λ/Δλ) of 25 for an Earth at 10 parsecs distance (Arnold et al., 2002).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Beichman et al., 2007
- Not checked yetcites Defrère et al., 2017
- Not checked yetcites Arnold et al., 2002
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“In an exoplanet observation, a red edge signal will not necessarily be atmospherically corrected in telescopic observations of a disk average spectrum.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“On Earth, large biogenic fluxes of gases from different ecosystems produce mixtures of gases that are chemically unstable on long timescales (Lovelock, 1965; Lovelock, 1975).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Lovelock, 1965
- Not checked yetcites Lovelock, 1975
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Further environmental corroboration would be the presence of potential substrates or side products for metabolisms that are being proposed as responsible for a biosignature gas.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Laboratory experiments and bioenergetic calculations show that >90% of the hydrogen is converted to methane if CO2 is not limiting (Kral et al., 1998; Kasting et al., 2001).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Kral et al., 1998
- Not checked yetcites Kasting et al., 2001
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If a biosignature is detected, direct corroborating evidence could take the form of either evidence of the biogenic source of that biosignature or there could be another, independent biosignature, suggesting the presence of biology that is not directly related to the other biosignature.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For biological pigments, the planet's environment may help predict the presence of a pigment due to its function, although there are many uncertainities.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“However, some recent laboratory simulations of serpentinization have produced no detectable CH4 (McCollom and Donaldson, 2016; Grozeva et al., 2017)”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites McCollom and Donaldson, 2016
- Not checked yetcites Grozeva et al., 2017
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Hitherto, such spectra have been generated for more specific cases that use Earth-like exoplanet atmosphere models rather than Exo-Earth System models per se (e.g., Robinson et al., 2011; Arney et al., 2016).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Robinson et al., 2011
- Not checked yetcites Arney et al., 2016
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Such models are corroborated through geochemical and isotopic paleoclimate proxies over geologic time (Berner, 2004; Mackenzie and Lerman, 2006; Kump et al., 2010; Langmuir and Broecker, 2012).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Berner, 2004 source
- Not checked yetcites Mackenzie and Lerman, 2006
- Not checked yetcites Kump et al., 2010
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“For example, in a dry CO2-rich atmosphere, O2 could potentially build up from photochemical destruction of CO2 (Gao et al., 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Gao et al., 2015
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Situations exist where a molecule that is predominantly biogenic on Earth could be an abiotic species, as noted in Table 4.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Also, the presence of biogenic N2O would be consistent with oxygenic photosynthesis because it derives from abundant organic matter produced from photosynthesis and oxidized forms of nitrogen.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“For example, light-harvesting pigments should absorb at wavelengths of available light with sufficient energy per photon to perform the necessary tasks of charge separation or proton pumping (Kiang et al., 2007b; Stomp et al., 2007).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Kiang et al., 2007b
- Not checked yetcites Stomp et al., 2007
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If O2 has been detected, the presence of CH4 would be an example of an independent biosignature, given that CH4 is not expected to be abundant in an O2 atmosphere unless there is a significant source, such as methanogenesis.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A SETI null signature only excludes extraterrestrial intelligence (ETI) and so provides limited prior information in a scheme for detecting biosignature gases from a global biosphere of non-ETI life.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For an exoplanet, detecting such multiphase disequilibria would require knowledge that an extensive liquid ocean exists by using techniques such as those described in section 3.3.2.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If H2O and O2 have been detected, an additional corroborating biosignature would be the red edge of a pigment that is widespread on the planet and essential to the function of photosynthetic production of O2.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Fischer–Tropsch reactions could cause subsequent abiotic reduction of inorganic carbon into methane and other abiotic organic compounds (Berndt et al., 1996; Etiope and Lollar, 2013; Guzman-Marmolejo et al., 2013).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Berndt et al., 1996
- Not checked yetcites Etiope and Lollar, 2013
- Not checked yetcites Guzman-Marmolejo et al., 2013
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“However, some biological pigments have colors that are fortuitous and unrelated to the light environment, but may be a function of the chemical environment, such as pH (Slonczewski et al., 2010).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Slonczewski et al., 2010
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For example, seasonal variations of a potentially biogenic gas (CH4) and substrate for photosynthesis (CO2), or pigment could be corroborative.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The simultaneous detection of O2 and CH4 would constitute a very compelling biosignature because of the short photochemical lifetime of CH4 in oxidizing atmospheres, as already described.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“If O2 builds up on a dry planet from CO2 photolysis (Gao et al., 2015), the dryness and presence of CO are diagnostics.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Gao et al., 2015
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Stellar parameters, for example, age and spectrum, provide further context for interpreting potential biosignatures through evaluating data likelihoods (Fig. 1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 5. Conclusions
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Similarly, in cases of abiotic O2 or O3 photochemical buildup on M-star planets (Domagal-Goldman et al., 2014; Tian et al., 2014), if real (Harman et al., 2015), a lack of CH4 would be expected.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Domagal-Goldman et al., 2014
- Not checked yetcites Tian et al., 2014
- Not checked yetcites Harman et al., 2015
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“and so should be accompanied by diagnostic photometric features associated with those hypothesized conditions.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Most biosignatures consist of spectral evidence of a biogenic gas (Table 4), and a deduction of its concentration or column abundance in an exoplanet atmosphere”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 5. Conclusions
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Spectral features near 3.5 μm (which became known as “Sinton bands”) were detected by ground-based telescopes and erroneously attributed to vegetation due to similarity with lichen spectra (Sinton, 1957; Sinton, 1959).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Sinton, 1957
- Not checked yetcites Sinton, 1959
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In general, a false positive tends to occur under circumstances that are at particular extremes of the parameter space we currently expect for rocky, atmosphere-bearing exoplanets”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“A proposed build up of tens or hundreds of bar of pO2 surface pressure on planets around M-stars because of a runaway greenhouse during premain sequence superluminous phase (Luger and Barnes, 2015), if real (Zahnle and Catling, 2017), would be indicated by a strong O4 dimer feature (Misra et al., 2014).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Luger and Barnes, 2015
- Not checked yetcites Zahnle and Catling, 2017
- Not checked yetcites Misra et al., 2014
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“which are potential false positives.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
In the paper
“Impacts that have reducing chemistry in the impact plume could generate substantial amounts of abiotic CH4 and NH3 (Zahnle et al., 2010)”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Zahnle et al., 2010
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Probably not a substantial claim. 98
- It may state two separate claims as one. 68
None of the sources cited for this claim have been checked yet.
In the paper
“Nonetheless, given the present stage of understanding and lack of data, the possibilities for P(life | Earth-like) range from life being very common to very rare, as has been much discussed in the literature”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Carter, 1983
- Not checked yetcites Spiegel and Turner, 2012
- Not checked yetcites Scharf and Cronin, 2016
plain- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“This assumption has been questioned because thick H2-rich atmospheres can provide warming far beyond the conventional HZ, even in interstellar space (Stevenson, 1999; Pierrehumbert and Gaidos, 2011; Seager, 2013).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Stevenson, 1999
- Not checked yetcites Pierrehumbert and Gaidos, 2011
- Not checked yetcites Seager, 2013
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“As we shall see, Bayes' theorem quickly reveals our current ignorance about life on exoplanets.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A related quantity can be derived from our formalism, which is the “base rate” frequency of occurrence of inhabited exoplanets around all main sequence stars in the galaxy”
- Also stated in: § 2. A Bayesian Framework for Biosignature Assessment and Life Detection · hedged
“Rather than a single exoplanet, this derived quantity would require multiple nondetections of life or even detections of multiple biospheres to be quantified, each observation causing an adjustment of priors.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Also stated in: § 2. A Bayesian Framework for Biosignature Assessment and Life Detection · hedged
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Hidden or cryptic biospheres are not practical candidates for life detection on exoplanets, so their consideration is not relevant to the empirical perspective of this article.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plain- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper may give no reason why it holds. It may state two separate claims as one.
In the paper
“Specifically, in the Drake equation, fl is defined as “the fraction of… [habitable] planets on which life actually develops” (Drake, 1965).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Drake, 1965
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“In assessing biosignatures, we face the problem of assigning a probability to whether an exoplanet is inhabited based on remote observations that will always be limited, especially given that in situ observations of even the nearest exoplanets are very far in the future (e.g., Lubin, 2016; Heller and Hippke, 2017; Manchester and Loeb, 2017).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
What the sources say
- Not checked yetcites Lubin, 2016
- Not checked yetcites Heller and Hippke, 2017
- Not checked yetcites Manchester and Loeb, 2017
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, the conventional HZ provides a guide based on real prior knowledge about CO2–H2O-rich planets from a real world—the Earth—whereas habitable H2-rich worlds remain hypothetical speculations.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus, this estimate would be significantly improved if we actually detect any life elsewhere or found environments on exoplanets to support the HZ concept.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“we expect that a reduced set of those variables—the so-called marginal variables in Bayesian statistics—will be important, whereas nuisance variables can be discarded, that is, “marginalized out.””
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The Earth is inhabited. Consequently, P(life | Earth-like) > 0, which is an aspect of empirical astronomy to which we now turn.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plainSingle case- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The prior conditional probabilities P(life | M-stars), etc. are currently unknown, except we know that P(life | G-stars) is nonzero because life exists on Earth.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plainSingle case- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Because extraterrestrial life has not yet been detected, the present state of scientific knowledge about the a priori probability of life occurring in the C-type that is an Earth-like, habitable exoplanet is based on two broad approaches: (1) consideration of the origin and persistence of life on a planet from laboratory and theoretical studies and (2) the fact that detectable life exists on Earth”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In reality, of course, the probabilities shown in Figure 1 will not be single numbers but functions of numerous parameters.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“Measurements such as the surface temperature or the detection of liquid water on the surface would provide direct confirmation that an exoplanet is habitable”
- Also stated in: § 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface · plain
“after the conventional definition of a habitable planet as one with a solid surface that has an extensive covering of liquid water”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Robinson, 2018
- Not checked yetcites Kasting et al., 1993
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Also stated in: § 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface · plain
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Other data given in Table 2 would increase confidence that the exoplanet is Earth-like in detail rather than just similar in size and mass, like Venus.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“A potentially inhabited exoplanet is embedded within the environment of its host star, so knowledge of the properties of the host star is critical for understanding exoplanet habitability.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Among basic physical properties, the exoplanet mass and radius provide the mean density of the exoplanet and the gravitational acceleration at the surface, g, which are very useful contextual parameters for the likelihoods and priors shown in Figure 1.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“the prior, P (life | C), would increase if we knew that an exoplanet surface has an ocean.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
In the paper
“so knowledge of the stellar rotation rate would help characterize the shortwave emission of a host star, particularly the large Lyman-α output at 121 nm”
- Also stated in: § 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system · plain
“which produces photons that drive photolysis reactions in planetary atmospheres, and feeds into estimated data likelihoods shown in Figure 1.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
What the sources say
- Not checked yetcites Linsky et al., 2013
plainconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Also stated in: § 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system · plain
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Clearly, the exoplanet effective blackbody temperature Teff can be calculated if the Bond albedo and incoming stellar flux are known.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Knowledge of the rotation rate of an exoplanet is highly desirable for a basic model of climate and habitability, and is context that would affect both likelihoods and priors in shown Figure 1.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“On Earth, deep-sea hyperthermophilic microbes can grow at 121°C and survive up to 130°C (Kashefi and Lovley, 2003).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Kashefi and Lovley, 2003
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Knowing about other planets and their properties in an extrasolar system could be important for deducing the formation history of the star–planet system, the possible orbital evolutionary path of the exoplanet of interest, and providing information that bears on climate stability.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.1. Component 1: stellar properties and “external” properties of the exoplanetary system
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Stellar and exoplanetary system external properties described for “component 1” provide context for understanding an exoplanet's habitability, but direct measurements concerning an exoplanet's “internal” properties are also needed to assess habitability, including bulk atmospheric composition and structure, climate, and surface state”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This Bayesian insight reveals how critical it is to evaluate the plausibility of a false positive detection of life.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 2. A Bayesian Framework for Biosignature Assessment and Life Detection
boosted- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence.
None of the sources cited for this claim have been checked yet.
In the paper
“On the modern Earth, values of parameters in Eq. 13 are S* = 1361 W/m2 (Kopp and Lean, 2011), AB = 0.3 (Palle et al., 2003; Stephens et al., 2015), Teff = 255 K, Tsurfe = 288 K, and ΔTgreenhouse = 33 K (Schmidt et al., 2010).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Kopp and Lean, 2011
- Not checked yetcites Palle et al., 2003
- Not checked yetcites Stephens et al., 2015
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In this carbonate–silicate hypothesis, a trend is predicted wherein HZ planets near the inner radius of the HZ should have relatively low pCO2, whereas HZ planets near the outer radius of the HZ should have higher pCO2.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Moreover, the extremes of Bond albedo in the solar system are comets at ∼0.04 and Enceladus at 0.89 (Howett et al., 2010; Encrenaz, 2014).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Howett et al., 2010
- Not checked yetcites Encrenaz, 2014
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Hence, the bulk atmospheric composition could affect thermal phase curves, and thus likelihoods of photometric data with and without life (Fig. 1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Furthermore, bulk composition fixes the specific heat capacity at constant pressure cp, which sets the dry adiabatic lapse rate Γad (decline of temperature with altitude in the convective part of a dry troposphere), given by Γad = g/cp.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The bulk atmospheric composition must be known to apply an equation of state.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
In the paper
“On a tidally locked body, atmospheres with bigger molar mass tend to have larger day–night temperature differences, narrower super-rotating jets, and smaller zonal wind speeds with more latitudinal variation (Zhang and Showman, 2017).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Zhang and Showman, 2017
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
““Carbon planets,” which are hypothesized to form in C-rich and O-poor protoplanetary disks, would also have solid surfaces but are predicted to be water-poor and uninhabitable to life as we know it (Bond et al., 2010; Carter-Bond et al., 2012; Elser et al., 2012; Moriarty et al., 2014).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Bond et al., 2010
- Not checked yetcites Carter-Bond et al., 2012
- Not checked yetcites Elser et al., 2012
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Planet formation models suggest that high C/O ratio disks could produce planets with iron cores, mantles of SiC or TiC, and diamond or graphite crusts.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Along with gravity, the bulk composition also determines the atmospheric scale height”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“On Earth, environmental feedbacks on CO2 maintain long-term habitability over ∼1 m.y. timescales through the carbonate–silicate geochemical cycle (Walker et al., 1981; Kasting and Catling, 2003; Krissansen-Totton and Catling, 2017; Krissansen-Totton et al., 2018a).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Walker et al., 1981
- Not checked yetcites Kasting and Catling, 2003
- Not checked yetcites Krissansen-Totton and Catling, 2017
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If such planets exist, reactions with carbon of any water delivered to the planet during accretion could preclude the presence of liquid water, although liquid hydrocarbons on the surface might be possible.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“However, glint alone just indicates a liquid, rather than water per se. For example, hydrocarbon lakes on Titan produce glint (Stephan et al., 2010; Soderblom et al., 2012).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Stephan et al., 2010
- Not checked yetcites Soderblom et al., 2012
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“With some knowledge of composition, the strength of weak bands can also be used to estimate pressure, for example, in early remote sensing of the solar system, the CO2 content found from the weak 1.6 μm band of CO2 was used to estimate the surface pressure on Mars (Owen and Kuiper, 1964).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Owen and Kuiper, 1964
plaindirectSingle case- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A 1/λ4 slope (where λ is wavelength) of the continuum in the UV-visible part of the spectrum could indicate Rayleigh scattering of particular molecular or aerosol species and possible transparency of an atmosphere (i.e., high single scattering albedo) caused by the haze-free chemistry of an oxidizing atmosphere.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Clouds indicate the presence of a volatile phase, which could be water if spectra are consistent with liquid water drops or water ice particles.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Hazes could be the photochemical products of volcanic or biogenic gases, which in certain chemical cases could indicate a volcanically active body (Kaltenegger et al., 2010; Misra et al., 2015) or a potentially inhabited early Earth-like body (Arney et al., 2016), respectively.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Kaltenegger et al., 2010
- Not checked yetcites Misra et al., 2015
- Not checked yetcites Arney et al., 2016
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Another potential antibiosignature is the coexistence of abundant H2 and CO2. These gases are a redox couple for microbial CH4 production, which molecular phylogenetic studies suggest may be one of the most primitive metabolisms on Earth (Weiss et al., 2016; Wolfe and Fournier, 2018).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Weiss et al., 2016
- Not checked yetcites Wolfe and Fournier, 2018
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Surface barometric pressure is an indicator of habitability (as sufficient pressure is required to prevent the rapid sublimation of any surface liquid water), and, when combined with g, gives the total atmospheric mass.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“One antibiosignature candidate is carbon monoxide (CO) (Zahnle et al., 2008; Gao et al., 2015), which has absorptions at 4.67 (strong), 2.34 (weak), and 1.58 μm (very weak) (Wang et al., 2016).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Zahnle et al., 2008
- Not checked yetcites Gao et al., 2015
- Not checked yetcites Wang et al., 2016
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“In general, the width of pressure-broadened molecular absorption bands can help to constrain atmospheric pressure, but is degenerate with composition, which also affects broadening (Chamberlain and Hunten, 1987, pp 175–176).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Chamberlain and Hunten, 1987
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“We should expect a habitable exoplanet with surficial liquid water to have substantial gas-phase H2O in its atmosphere as a result of evaporation and so numerous H2O vapor absorption bands should be present.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Clouds and hazes are observed on all planets in the solar system with thick atmospheres, although planets such as Earth are much less cloudy than giant planets.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Oxidizing atmospheres can contain widespread H2SO4 aerosols but not Titan-like global organic hazes.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
It may state two separate claims as one.
In the paper
“Finally, for the specific case of tidally locked rocky exoplanets, the day–night temperature gradient depends on surface pressure, equilibrium temperature, and composition”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Koll and Abbot, 2016
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The vegetation red edge remains the only well-accepted surface biosignature and is caused by red absorbance by chlorophyll a in plant leaves and scattering in the NIR where the pigment does not absorb.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“The most popular metric is the normalized difference vegetation index (NDVI) = (RNIR − RRED)/(RNIR + RRED) (Huete et al., 1994; Myneni et al., 1995; Myneni et al., 1997; Tucker et al., 2005), where RRED is the surface reflectance in the red band and RNIR is the reflectance in the NIR band.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Huete et al., 1994
- Not checked yetcites Myneni et al., 1995
- Not checked yetcites Tucker et al., 2005
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The Earth-observing satellites Moderate Resolution Imaging Spectrometer (MODIS) and the Landsat Thematic Mapper (TM), which were designed to map vegetation, use a 630–690 nm red band.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“Similar retrievals are being considered for the search for biosignatures on Earth-like worlds (von Paris et al., 2013; Barstow and Irwin, 2016; Barstow et al., 2016).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites von Paris et al., 2013
- Not checked yetcites Barstow and Irwin, 2016
- Not checked yetcites Barstow et al., 2016
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, in general, a redox reaction as a source of metabolic energy, whether derived from environmental chemical gradients or from excitation of electrons by photons, is a universal aspect of chemistry that should apply to life anywhere.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The abundance of a potentially biogenic gas can be determined most simply in the UV, visible or NIR where reflected light dominates over thermal emission from a planetary atmosphere and surface, so that thermal IR can be ignored.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“For the NIR band, plant leaves have an NIR reflectance plateau across ∼760–1100 nm; however, this range is also impacted by water absorbance bands.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus, iterative procedures would fit a spectrum to a line or multiple lines to estimate the gas abundance(s) if the spectral resolution and signal-to-noise are sufficient.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Most currently accepted biosignatures consist of spectral evidence of a biogenic gas molecule.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
- Rests on an assumption: Earth's biosphere and its biosignatures are suitable analogs for interpreting potential exoplanet biosignatures.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“For the red, the band is best centered around the peak pigment absorbance at 650–680 nm.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“MODIS and Landsat TM precisely target a 780–900 nm NIR band to avoid overlap with the red edge and with water.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“If unsaturated and saturated lines of a constituent are measured, “curve of growth” laboratory data (of the increasing absorption with mass path of absorber) can be used to find the column abundance of the gas, N0.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Among phototrophs, the red edge is not unique in expressing these functions but it is widespread over Earth's surface and lacks any strong false positives for life.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In the general case, an effective airmass will depend on an exoplanet's phase (e.g., full or quarter disk illumination) and the way brightness varies across the disk.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Earth-observing satellites quantify the red edge by using the contrast between visible and NIR spectral regions.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For gases, a distinct spectral feature or number of features would identify the presence of a potential biogenic gas and further analysis would deduce a concentration or column abundance of the molecule in an exoplanet atmosphere.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds. It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“The lack of SO2 and HCl spectral absorption has been used as evidence for absence of volcanic activity on Mars (Hartogh et al., 2010; Krasnopolsky, 2012; Khayat et al., 2017).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
What the sources say
- Not checked yetcites Hartogh et al., 2010
- Not checked yetcites Krasnopolsky, 2012
- Not checked yetcites Khayat et al., 2017
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In principle, if the line width ΔνL comes from pressure broadening, then, assuming temperature T is known or can be estimated, one can calculate a total pressure p and a volume mixing ratio of a biosignature gas, ci = pi/p, where pi is the partial pressure of the absorbing gas, defined by the ideal gas law and Dalton's law:”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plainconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In a more modern treatment, we know enough about the spectral structure of bands to account for line saturation and overlap explicitly to determine gas abundances from the spectrum of multiple lines.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The colors of other pigments may be fortuitous without a clear function with respect to light interactions.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A quantitative framework for evaluating surface biosignatures remains unclear.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, the prominent wavelength bands will rely on molecular energy transduction constraints and the efficiencies, which result from contingent evolutionary pathways, including competitive survival strategies.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If detected, seasonal variations would be especially informative.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Clearly, pigments whose role is light harvesting and screening of ionizing radiation or excess light must have a spectral absorbance that depends on the available light.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“Similar arguments about CH4:H2 ratios have also been applied to life within the solar system, on both Enceladus (Waite et al., 2017) and Mars (Sholes et al., 2017).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Waite et al., 2017
- Not checked yetcites Sholes et al., 2017
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Except for chirality and the terrestrial vegetation red edge, the uniqueness of the other surface spectral signatures and potential for false positives have yet to be scrutinized.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds. It may state two separate claims as one.
In the paper
“Also, some pigments adapt colors in real time to fluctuating colors of light (Kehoe and Gutu, 2006).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Kehoe and Gutu, 2006
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“Biogenic surface spectral features are also the result of ecological signaling (Schwieterman et al., 2015a), community signatures (Parenteau et al., 2015), chiral molecules (Sparks et al., 2009; Sparks et al., 2012), and the bidirectional reflectance distribution function that accounts for angle-dependent reflectivity (Doughty and Wolf, 2010).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Schwieterman et al., 2015a
- Not checked yetcites Parenteau et al., 2015
- Not checked yetcites Sparks et al., 2009
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Moreover, chlorophyll pigments have recently been discovered in cyanobacteria, tuned to absorb in the far red/NIR as long ∼0.77 μm (Chen, 2014; Li and Chen, 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Chen, 2014
- Not checked yetcites Li and Chen, 2015
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Color variations on a rotating planet might provide circumstantial support for life and would be additional photometric “data” shown in Figure 1.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
In the paper
“They found that the red edge detectability ranged from 1% to 12% in observations and models.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Arnold (2008)
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“Pigments that absorb in the visible include, for example, cytochromes (∼0.40 μm), carotenoids (0.28–0.55 μm), cyanobacterial and chloroplast accessory pigments (0.40–0.74 μm), bacteriochlorophyll pigments (0.74–1.03 μm), and retinal pigments (0.53–0.63 μm) (DasSarma, 2006; Hegde et al., 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites DasSarma, 2006
- Not checked yetcites Hegde et al., 2015
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Biological denitrification produces N2O, but (on Earth, at least) it also produces even more N2, so that the presence of the two gases together might support the idea that N2O is biological.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Moreover, some pigments may be stratified and tuned depending on the environmental conditions.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“On the current Earth, the ratio CO2:CH4:H2 is ∼400:1.8:0.5, where the numbers are in ppmv.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
None of the sources cited for this claim have been checked yet.
In the paper
“In addition, if CH4:CO2 ratios exceed ∼0.1, and there is adequate UV flux from the star, an organic haze is produced (Trainer et al., 2006; Haqq-Misra et al., 2008; Arney et al., 2016), which may decrease biological productivity through an antigreenhouse effect on the climate (Haqq-Misra et al., 2008).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Trainer et al., 2006
- Not checked yetcites Haqq-Misra et al., 2008
- Not checked yetcites Arney et al., 2016
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“A methodology to quantify thermodynamic chemical disequilibrium has been established and could be applied (Krissansen-Totton et al., 2016a, 2018b).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Krissansen-Totton et al., 2016a
- Not checked yetcites Krissansen-Totton et al., 2018b
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Alternatively (or additionally), the inference of surficial liquid water could come from abundant H2O vapor lines in the spectrum, evidence of glint, or polarized reflected light (discussed in section 3.3.2).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“On an oxidized world, photosynthesis requires CO2 as a chemical substrate, so detection of CO2 would support the possibility that O2 is a biosignature.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The most fundamental evidence supporting inhabitation would be a surface emission temperature, Tsurfe, that allows stable liquid water on an exoplanet, which would increase the prior P(life | C) and improve modeling of the data likelihoods shown in Figure 1.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds. It may state two separate claims as one.
- Rests on an assumption: The Bayesian framework with priors and likelihoods can be meaningfully applied to exoplanet biosignature assessment.
In the paper
“In contrast, a small amount of CH4 in a hydrogen-rich atmosphere (a high H2:CH4 ratio) could result from abiotic chemistry, as found today on the giant planets of the solar system (Irwin, 2009), and the interpretation of CH4 as a biosignature would be doubtful because such atmospheres could be primordial.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Irwin, 2009
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“To calculate chemical disequilibrium properly for an Exo-Earth, one must consider all fluid phases because the largest source of disequilibrium in Earth's atmosphere–ocean system is attributable to the coexistence of N2, O2, and liquid water, as quantified by Krissansen-Totton et al. (2016a) and qualitatively noted by, for example, Lewis and Randall (1923, pp 567–568) and Emerson and Hedges (2008,”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Krissansen-Totton et al., 2016a
- Not checked yetcites Lewis and Randall (1923)
- Not checked yetcites Emerson and Hedges (2008)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“There is not yet a consensus on why the vegetation red edge is red, although some argue that chlorophyll a evolved to exploit the large number of photons in the red part of the Sun's spectrum convolved with the free energy that each converted photon contributes and transmission of Earth's atmosphere (Bjorn, 1976; Milo, 2009; Marosvolgyi and van Gorkom, 2010; Björn and Ghiradella, 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Bjorn, 1976
- Not checked yetcites Milo, 2009
- Not checked yetcites Marosvolgyi and van Gorkom, 2010
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Of course, considerable work still needs to be done to understand the coevolution of biogeochemical cycles and atmospheric composition on Earth, which is being addressed by using “Earth System” models.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“Such temporal variations occur on Earth (e.g., Schlesinger and Bernhardt, 2013, Chap. 11).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Schlesinger and Bernhardt, 2013
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Since organisms can have more than one strategy for survival, and we cannot measure environmental variables like pH remotely, constraining the suitable environments for these alternative biosignatures is a matter of more research.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A general procedue for excluding false positives of biogenic processes might include the following steps. First, it is necessary to identify a plausible abiotic source. Second, the abiotic source must be detected or supported by corroborating evidence.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Other pigments may be related to nano- or microstructure and be purely evolutionary contingent.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
In the paper
“Zahnle and Catling (2017) note the tendency of oxygen to photochemically buffer H:O loss at 2:1 ratio at high escape rates.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Zahnle and Catling (2017)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“Considerable research has been devoted to identifying abiotic sources of O2 and its photochemical product O3 (Hu et al., 2012b; Tian et al., 2014; Domagal-Goldman et al., 2014; Wordsworth and Pierrehumbert, 2014; Gao et al., 2015; Harman et al. 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Hu et al., 2012b
- Not checked yetcites Tian et al., 2014
- Not checked yetcites Domagal-Goldman et al., 2014
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For example, a better constraint of one particular parameter could remove degeneracies (i.e., where two or more parameters have similar overall effects) and produce a better model fit to the spectrum.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The latter is because ETI machines can exist on an airless moon or planet.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“False positives need to be evaluated, as noted in Figure 2, and quantified by a likelihood P(D | C, no life) in our framework (Fig. 1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
- Rests on an assumption: The Bayesian framework with priors and likelihoods can be meaningfully applied to exoplanet biosignature assessment.
In the paper
“Bacteria such as the radiotolerant Deinococcus radiodurans manufacture antioxidant carotenoids, such as deinoxanthin, in response to UV, and extraterrestrial microbe-like life may have similar physiological response (Tian and Hua, 2010).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
What the sources say
- Not checked yetcites Tian and Hua, 2010
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“A short lifetime (∼10 years) and an inferred large flux into the atmosphere are the case for CH4 in Earth's current O2-rich atmosphere.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In the future, an Exo-Earth System model could be configured in the form of an inverse fit to spectra or photometry data from exoplanets (Fig. 1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedged- Asserted: fails — The authors may not put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The authors may not put it forward as true. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The latter would necessarily use radiative transfer; models could also include atmospheric and ocean dynamics.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“An investigation of covariance of uncertain parameters in such a fit would show which parameters we need to know better from future observations to improve confidence that the spectrum really represents biology.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Ultimately, such forward models would be used to generate a synthetic reflectance or transmission spectrum and Bayesian likelihoods, P(D | C, life) and P(D | C, no life) (Fig. 1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
- Rests on an assumption: The Bayesian framework with priors and likelihoods can be meaningfully applied to exoplanet biosignature assessment.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“If just gaseous components are known for an exoplanet, it may be possible to estimate their kinetic instability, that is, residence time against photochemical destruction, and deduce whether a large, potentially biogenic source is needed.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: unclear — It is unclear why the paper says it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“It is notable that neutral O2 is undetectable on Venus, the one case of a postrunaway greenhouse in our solar system, where oxygen must have been either lost efficiently (Zahnle and Kasting, 1986; Zahnle et al., 1988) or taken up by a magma ocean (Hamano et al., 2013), which may also occur on exoplanets (Schaefer et al., 2016).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Zahnle and Kasting, 1986
- Not checked yetcites Zahnle et al., 1988
- Not checked yetcites Hamano et al., 2013
plaindirectSingle case- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“In one such case, oceans are hypothesized to vaporize and be lost from HZ planets in the luminous premain sequence phases of M dwarfs, leaving behind very O2-rich atmospheres (Luger and Barnes, 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Luger and Barnes, 2015
hedgedconditional- Asserted: fails — The authors may not put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The authors may not put it forward as true. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, relatively little attention has been given to abiotic scenarios where other candidate biosignature gases could be significant.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The aforementioned discussion of non-ETI biosignatures indicates the obvious need to understand the biogeochemistry of exoplanets to interpret biosignatures through calculations of data likelihoods and interpret the context for a Bayesian prior, P(life | C), needed for the overall biosignature framework (Fig. 1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
- Rests on an assumption: The Bayesian framework with priors and likelihoods can be meaningfully applied to exoplanet biosignature assessment.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“With data of sufficient fidelity, a Bayesian fit would allow for quantitative constraints on possible gas fluxes that are needed to support a potential biosignature gas.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
- Rests on an assumption: Future exoplanet observations can achieve sufficient spectral resolution and signal-to-noise to detect and quantify biosignature gases and surface features.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus, how much CH4 can be produced abiotically on an exoplanet as a false positive remains a matter of research.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
- Rests on an assumption: The geological process of serpentinization produces H2 when liquid H2O oxidizes iron in rocks.
- Rests on an assumption: More than 90% of CH4 on Earth has a direct biogenic source or comes indirectly from biology through thermal breakdown of old organic matter.
In the paper
“For example, as reviewed by Meadows et al. (2018, in this issue), several theoretical studies have suggested that abiotic, bulk O2 could be present under certain hypothesized circumstances.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Meadows et al. (2018)
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A positive SETI signal provides certainty about the presence of ETI, by definition, but does not necessarily indicate that a biosphere or that biosignature gases are present.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“suggesting that CH4 may have arisen in earlier experiments from organic contamination (McCollom, 2016).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites McCollom, 2016
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“It has also been proposed that O2 could build up abiotically on highly irradiated planets as a result of escape of hydrogen from water photolysis (Luger and Barnes, 2015).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Luger and Barnes, 2015
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The extent to which purely hypothetical ideas about O2 buildup are realized remains to be determined, but their possibility demands caution.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For example, a null SETI signal detected at 100 Ma from Earth by an ETI civilization observing our planet remotely should not have affected their priors for the existence of non-ETI life on Earth at all because a null SETI signal excludes ETI only.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A model could incorporate how the interior thermal evolution of a planet couples to mantle processes and outgassing of volcanic and metamorphic gases.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For exoplanets, we conceive of “Exo-Earth System” models, as mentioned earlier, that would couple a surface biosphere to atmospheric chemistry and climate.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Hence, exoplanet priors for ETI are potentially completely different to the habitable requirements for a non-ETI biosphere that produces gas or pigment biosignatures; ETI priors are also subject to considerably more speculation, given unknown evolutionary and sociological factors.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: unclear — It is unclear whether it could be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“Similarly, initial reports of ammonia and methane in the NIR reflection spectrum of the polar caps of Mars observed by the Mariner 7 flyby were subsequently shown to be due to solid CO2 at the surface (Herr and Pimentel, 1969).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Herr and Pimentel, 1969
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Pigments and surface biosignatures (Table 5) represent potentially confirmatory biosignatures.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 5. Conclusions
hedged- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper may give no reason why it holds.
In the paper
“Their set of five basic probability levels are very likely 90–100%, likely 66–100%, about as likely as not 33–66%, unlikely 0–33%, and very unlikely 0–10% (Stocker et al., 2013, their Box TS.1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 4. A Proposed System of Confidence Levels of Life Detection on Exoplanets
What the sources say
- Not checked yetcites Stocker et al., 2013
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“Hypothetical planets that lack noncondensable N2 (if that is cosmochemically plausible) and build up O2 from water vapor destruction and loss (Wordsworth and Pierrehumbert, 2014) would lack the N4 dimer signatures and may have strong O4.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Wordsworth and Pierrehumbert, 2014
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“Subsequent work showed that the Sinton bands were due to terrestrial water with deuterium, HDO (Rea et al., 1965).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Rea et al., 1965
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Covariances of parameters identified in inverse modeling with a chemical-radiative atmospheric forward model would help prioritize which parameters are most important for follow-up observations.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 5. Conclusions
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: fails — It may be too vague to check against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
In the paper
“When an exoplanet hosts a moon with its own atmosphere, a single spectrum that includes both moon and exoplanet could end up resembling a mixture of both atmospheres and perhaps could generate chemical disequilibrium false positives (Rein et al., 2014).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Rein et al., 2014
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The biogenic nature of such molecules must be assessed through the environmental context deduced through components 1 and 2 and also any corroborating evidence such as other information on atmospheric composition.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 5. Conclusions
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“These include the thermal emittance and Bond albedo, which are needed to estimate the surface temperature (i.e., whether liquid water is stable on the surface) as opposed to merely being in a HZ.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 5. Conclusions
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
In the paper
“Here, O2 may be formed abiotically by collision of energetic water ions with oxygen-containing minerals on the comet's surface (Yao and Giapis, 2017).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Yao and Giapis, 2017
hedgedconditionalSingle case- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“For example, clathrates in cold regions could melt and input methane into an atmosphere (Levi et al., 2014).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.4. Component 4: Excluding explicit false positives
What the sources say
- Not checked yetcites Levi et al., 2014
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Models of atmospheric composition and climate are an important part of such an assessment.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 5. Conclusions
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“but time-variable photometry may also be useful (Fig. 1).”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 5. Conclusions
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“If high accuracy is known at the upper and lower bounds of probabilities, the IPCC also recommends “virtually certain” for 99–100%, “extremely likely” for 95–100%, “extremely unlikely” for 0–5% probability, and “exceptionally unlikely” for 0–1%.”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 4. A Proposed System of Confidence Levels of Life Detection on Exoplanets
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
The paper relies on this without support.
Life produces gases and other substances, such as pigments, that can have distinct spectral or photometric signatures.
“Life produces gases and other substances, such as pigments, which can have distinct spectral or photometric signatures.”
The authors state this as an assumption.
For the framework, the presence of life is treated as a binary variable: a remotely detectable surface biosphere is either present or absent.
“We take the presence of life to mean the existence of a surface biosphere that is remotely detectable, which we treat as a binary variable, that is, either an exoplanet biosphere is present or it is not.”
“Because we assume that a biosphere is either present on an exoplanet or absent, it follows that these two are priors are related by”
The authors state this as an assumption.
P(life|O-stars) is negligible.
“Most people would also consider it reasonable to assume that P(life | O-stars) is negligible because O-stars have main sequence lifetimes that range from less than one to a few million years (Weidner and Vink, 2010).”
The authors state this as an assumption.
In the absence of other information, a prior of P(life | Earth-like) = 0.5 is a practical starting point for an Earth-like planet in the HZ of a Sun-like star.
“in the absence of any other information, if we found an Earth-like planet in the HZ of a Sun-like star, a starting point—based on empirical data of our current solar system—might be to assume a prior of P(life | Earth-like) = 0.5”
The paper relies on this without support.
Earth's biosphere and its biosignatures are suitable analogs for interpreting potential exoplanet biosignatures.
“Most currently accepted biosignatures consist of spectral evidence of a biogenic gas molecule.”
The paper relies on this without support.
The Bayesian framework with priors and likelihoods can be meaningfully applied to exoplanet biosignature assessment.
“Environmental information could be used to improve estimates of data likelihoods or alter the priors shown in Figure 1, whereas new biosignature data would add to the “data” box of Figure 1.”
The paper relies on this without support.
Future exoplanet observations can achieve sufficient spectral resolution and signal-to-noise to detect and quantify biosignature gases and surface features.
“With data of sufficient fidelity, a Bayesian fit would allow for quantitative constraints on possible gas fluxes that are needed to support a potential biosignature gas.”
The paper relies on this without support.
The geological process of serpentinization produces H2 when liquid H2O oxidizes iron in rocks.
“The geological process of serpentinization produces H2 when liquid H2O oxidizes iron in rocks.”
The paper relies on this without support.
More than 90% of CH4 on Earth has a direct biogenic source or comes indirectly from biology through thermal breakdown of old organic matter.
“More than 90% of CH4 on Earth has a direct biogenic source or comes indirectly from biology through thermal breakdown of old organic matter”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
In the citing paper
“In the Archean, high CH4 should be readily detectable (35), and CO2 has abundant absorption features (36).”
From Disequilibrium biosignatures over Earth history and implications for detecting exoplanet life (2018) · cites this paper as [36]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Rated major: it would touch a result — a value a result rests on, reported and recomputed p-values on opposite sides of the significance level, two passages that conflict with no sign which is right, or a cited work retracted before this paper was published.
In the paper
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.2. Component 2: the “internal” properties of the exoplanet atmosphere, climate, and surface
“| Organic haze | Continuum opacity in visible-NIR | Indicates a reducing atmosphere with CO2/CH4 < 0.1 |”
§ Exoplanet Biosignatures: A Framework for Their Assessment > 3. Input Components in a Framework of Observing Exoplanet Biosignatures > 3.3. Component 3: search for potential biosignatures in the spectral data
“if CH4:CO2 ratios exceed ∼0.1, and there is adequate UV flux from the star, an organic haze is produced”
Citations
Cites
Inverse Methods for Atmospheric Sounding: Theory and Practice
Rodgers, C. D. (2000) · Series on Atmospheric, Oceanic and Planetary Physics · doi:10.1142/3171 · Cited by 3,057
The rise of oxygen in Earth's early ocean and atmosphere
Lyons, T. W., Reinhard, C. T., & Planavsky, N. J. (2014) · Nature · doi:10.1038/nature13068 · Cited by 2,810 · cited 1×
“For example, in the case of Earth, O2 was not detectable in our atmosphere until about halfway through Earth’s history (Lyons et al., 2014).”
BackgroundHabitable Zones around Main Sequence Stars
Kasting, J. F., Whitmire, D. P., & Reynolds, R. T. (1993) · Icarus · doi:10.1006/icar.1993.1010 · Cited by 2,501 · cited 3×
“Regarding habitability, the ubiquitous concept of the HZ is built upon the assumption that P(life jC) is higher where the context is an exoplanet orbiting within a certain range of star–planet distances (Kasting et al., 1993; Kasting, 1997; Kopparapu et al., 2013).”
BackgroundAn extended AVHRR 8‐km NDVI dataset compatible with MODIS and SPOT vegetation NDVI data
Tucker, C. J., Pinzón, J. E. D., Brown, M. E., Slayback, D. A., Pak, E. W., Mahoney, R. L., Vermote, E. F., & Saleous, N. (2005) · International Journal of Remote Sensing · doi:10.1080/01431160500168686 · Cited by 2,310
A negative feedback mechanism for the long‐term stabilization of Earth's surface temperature
Walker, J. C. G., Hays, P. B., & Kasting, J. F. (1981) · Journal of Geophysical Research: Oceans · doi:10.1029/jc086ic10p09776 · Cited by 2,310
The Planet‐Metallicity Correlation
Fischer, D. A., & Valenti, J. A. (2005) · The Astrophysical Journal · doi:10.1086/428383 · Cited by 1,641
HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: NEW ESTIMATES
Kopparapu, R. K., Ramirez, R., Kasting, J. F., Eymet, V., Robinson, T. D., Mahadevan, S., Terrien, R. C., Domagal-Goldman, S., Meadows, V., & Deshpande, R. (2013) · The Astrophysical Journal · doi:10.1088/0004-637x/765/2/131 · Cited by 1,615 · cited 10×
“Indeed, the most common stars, M dwarfs, have a lower flux in the near-UV than the Sun, so that for the same biogenic CH4 flux as the Earth, the CH4 abundance reaches a higher and more detectable level depending upon the exact SED (Segura et al., 2005; Rugheimer et al., 2015).”
BackgroundInfluentialSelf-citationSeven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
Gillon, M., Triaud, A. H. M. J., Demory, B.-O., Jehin, E., Agol, E., Deck, K. M., Lederer, S. M., de Wit, J., Burdanov, A., Ingalls, J. G., et al. (2017) · Nature · doi:10.1038/nature21360 · Cited by 1,555
Rauer, H., Catala, C., Aerts, C., Appourchaux, T. P., Benz, W., Brandeker, A., Christensen-Dalsgaard, J., Deleuil, M., Gizon, L., Goupil, M. J., et al. (2014) · Experimental Astronomy · doi:10.1007/s10686-014-9383-4 · Cited by 1,390
Duchêne, G., & Kraus, A. L. (2013) · Annual Review of Astronomy and Astrophysics · doi:10.1146/annurev-astro-081710-102602 · Cited by 1,353
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Cited by
Sorted by citations
Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life
Schwieterman, E. W., Kiang, N. Y., Parenteau, M. N., Harman, C. E., DasSarma, S., Fisher, T. M., Arney, G. N., Hartnett, H. E., Reinhard, C. T., Olson, S. L., et al. (2018) · Astrobiology · doi:10.1089/ast.2017.1729 · Cited by 630
Self-citationExoplanetary Atmospheres: Key Insights, Challenges, and Prospects
Madhusudhan, N. (2019) · Annual Review of Astronomy and Astrophysics · doi:10.1146/annurev-astro-081817-051846 · Cited by 352
Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its Environment
Meadows, V., Reinhard, C. T., Arney, G., Parenteau, M. N., Schwieterman, E. W., Domagal-Goldman, S. D., Lincowski, A., Stapelfeldt, K. R., Rauer, H., DasSarma, S., et al. (2018) · Astrobiology · doi:10.1089/ast.2017.1727 · Cited by 341
Self-citationCarbon-bearing Molecules in a Possible Hycean Atmosphere
Madhusudhan, N., Sarkar, S., Constantinou, S., Holmberg, M., Piette, A. A. A., & Moses, J. I. (2023) · The Astrophysical Journal Letters · doi:10.3847/2041-8213/acf577 · Cited by 282
Impact of space weather on climate and habitability of terrestrial-type exoplanets
Airapetian, V. S., Barnes, R., Cohen, O., Collinson, G. A., Danchi, W. C., Dong, C., C, A. D. D. G., France, K., Garcia-Sage, K., Glocer, A., et al. (2019) · International Journal of Astrobiology · doi:10.1017/s1473550419000132 · Cited by 288
Metadata
- Authors
- Catling, D. C., Krissansen-Totton, J., Kiang, N. Y., Crisp, D., Robinson, T. D., DasSarma, S., Rushby, A. J., Del Genio, A., Bains, W., & Domagal-Goldman, S.
- Affiliations
- University of Washington (US)
- Astrobiology Program, Department of Earth and Space Sciences, University of Washington, Seattle, Washington.
- Goddard Institute for Space Studies (US)
- California Institute of Technology (US)
- University of California, Santa Cruz (US)
- University of Maryland, Baltimore (US)
- Ames Research Center (US)
- NASA Goddard Institute for Space Studies, New York, New York.
- Massachusetts Institute of Technology (US)
- Goddard Space Flight Center (US)
- Corresponding author
- Catling, David C.
- Venue
- Astrobiology
- Publisher
- SAGE Publications
- Published
- 2018-06
- Volume
- 18
- Issue
- 6
- Pages
- 709-738
- ISSN
- 1531-1074 (ISSN-L)
- 1557-8070
- PMC
- PMC6049621
- OpenAlex
- W2949593113
- Cited by
- 225
- References
- 258
- Citations by year
- 2026: 17 · 2025: 30 · 2024: 21 · 2023: 30 · 2022: 29 · 2021: 28 · 2020: 16 · 2019: 27 · 2018: 25
- FWCI
- 12.86
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- cc-by-nc
- Locations
- Astrobiology (publishedVersion, cc-by-nc)
- Europe PMC (PubMed Central) (publishedVersion, other-oa)
- PubMed Central (publishedVersion, cc-by-nc)
- PubMed (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- arXiv (Cornell University)
- Funders
- National Aeronautics and Space Administration (NNX15AR63H, NNX15AM07G, Exobiology grant NNX15AM07G)
- Universities Space Research Association
- University of Oxford
- NASA Astrobiology Institute (NNX15AM07G)
- Ames Research Center
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Space Science and Extraterrestrial Life
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Physical Sciences › Earth and Planetary Sciences › Space and Planetary Science › Planetary Science and Exploration
- Keywords
- exoplanet biosignatures, habitability, false positives, Drake equation, exoplanet characterization, planetary climate
- MeSH terms
- Origin of Life, Bayes Theorem, Extraterrestrial Environment, Planets, Exobiology
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
A language model drew the claims from the paper on 2026-10-10, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
A second model labelled each claim on 2026-10-10 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
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