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The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth
Open accessAbstract
Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8–2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7–2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO 2 . Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets. Key Words: Haze—Archean Earth—Exoplanets—Spectra—Biosignatures—Planetary habitability. Astrobiology 16, 873–899.
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TL;DR
Coupled climate-photochemical-microphysical simulations of hazy Archean Earth show that organic haze can cool the surface by about 20 K but still permit habitable temperatures with liquid surface water, because thick hazes self-limit via UV self-shielding. The haze also strongly shields surface UV and produces distinctive spectral features, suggesting hydrocarbon haze may be a biologically mediated spectral biosignature on anoxic, CO₂-rich exoplanets.
Key findings
- Hazy Archean climates were cold but likely habitable: for Cases A–D, stabilized surface temperatures with haze were 263, 274, 262, and 251 K, and with ice-albedo feedback 257, 271, 257, and 241 K, all above the adopted 248 K habitability threshold; haze cooling reached up to ∼20 K, with maximum haze optical thickness leveling off at τ ∼ 5 at 200 nm.
- Haze is self-limiting: optically thicker hazes shield CH₄ from photolysis, shutting down haze formation and preventing catastrophic cooling; the CH₄/CO₂ ratios needed to initiate haze formation were 0.18, 0.15, 0.19, and 0.28 for Cases A–D.
- UV shielding was substantial: for Case B with CH₄/CO₂ = 0.21, surface UVC flux was about 0.03 W/m² at SZA = 60° and 0.22 W/m² at SZA = 0°, compared with 0.93 and 2.62 W/m² for the haze-free case, a reduction of about 97%; this may have allowed survival of land-based organisms 2.7–2.6 billion years ago.
- Hazy Archean Earth would be a “pale orange dot,” with a broad UV absorption signature, a 6 μm transit-transmission haze feature, and a weaker 3 μm feature; the CH₄ flux needed to initiate haze was about 1 × 10¹¹ to 3 × 10¹¹ molecules/cm²/s, far above estimated maximum abiotic serpentinization fluxes of 6.8 × 10⁸ and 1.3 × 10⁹ molecules/cm²/s for 1 and 5 Earth-mass rocky planets.
Methods
- Used the coupled 1-D photochemical-climate model Atmos and the 1-D radiative transfer model SMART; the photochemical model has 200 plane-parallel layers from the surface to 100 km, 76 chemical species, and fractal hydrocarbon haze microphysics, while the climate model uses correlated-k absorption and a δ-2-stream radiative transfer scheme, iterating between models to convergence.
- Simulated four Archean cases spanning pCO₂ = 0.0036–0.018 bar and surface pressure = 0.5–1 bar, with solar constant at 2.7 Ga = 0.81 S/S₀, surface O₂ = 1.0 × 10⁻⁸, and varied CH₄/CO₂; about 60 coupled Atmos runs were required.
- Generated synthetic reflectance, thermal emission, and transit transmission spectra with SMART, including binned haze particle modes and, for Case B, tests with water clouds.
Limitations
- Stated in paper: the climate model could only be run to about 80 km while the photochemical model extends to 100 km, with isoprofiles above the climate grid; sensitivity tests showed <5% difference in largest haze particles and <0.5 K surface temperature effect. Older CH₄ coefficients may overestimate surface temperature by ≲5 K, while the model underpredicts Archean temperature by about 2–5 K compared with 3-D models, so these may cancel.
- Stated in paper: the 1-D model lacks atmospheric circulation, precipitation, cloud formation, cloud scattering and absorption, and long-wave cloud radiative forcing; comparison with GCMs suggests the presented temperatures may be underestimates by about 3–5 K, and ice-albedo feedback, haze deposition, haze circulation, and cloud feedbacks are left to future GCM studies.
- Stated in paper and evident from text: haze formation chemistry is not well understood, and the model assumes C₄H₂ and C₅H₄ condense directly to haze particles, possibly overestimating aerosol formation; only one Archean haze refractive index measurement exists, at 532 nm, and the study uses Titan-like Khare optical constants; NH₃ was not included in the photochemical scheme; nominal haze spectra exclude water clouds.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > Abstract
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In the paper
“We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > Abstract
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In the paper
“but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“reducing surface UV flux by about 97% compared to a haze-free planet”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIn the paper
“The haze can produce a stronger UV shield compared to the low O2 atmosphere (0.1% PAL) proposed recently by Planavsky et al. (2014) for our atmospheric assumptions.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
What the sources say
- Not checked yetcites Planavsky et al., 2014
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In the paper
“By using the updated habitability threshold of Tsurf > 248 K, all our cases even with thick hazes are habitable.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Rests on an assumption: A planet with any nonzero fraction of open ocean is habitable.
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In the paper
“The Bond albedos produced in these cases including haze are 0.26, 0.24, 0.26, and 0.29.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
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In the paper
“In the hotter atmosphere, τcoag is smaller than τsed through most of the atmospheric column.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
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In the paper
“As the haze gets optically thicker, absorption of UV photons produces an atmospheric temperature inversion (Fig. 5) similar to that produced by ozone in the modern atmosphere.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe 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 insignificant haze present in the CH4/CO2 = 0.1 atmosphere is spectrally indistinguishable from an atmosphere with no haze.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results
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- Probably not a substantial claim. 40
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In the paper
“The particle mode sizes we use span from 0.001 to 2 μm; larger particles do not exist in our atmospheres due to rainout.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.2. The SMART model
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably 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.
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“The largest particles produced by the 250 K atmosphere have a geometric radius of 0.8 μm compared to 0.65 μm radius particles for the 200 K atmosphere.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
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In the paper
“In contrast, the surface UVC flux under a haze for Case B (CH4/CO2 = 0.21) would have been about 0.03 W/m2 for SZA = 60° and 0.22 W/m2 for SZA = 0°.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
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In the paper
“A modest amount of O2 in the Proterozoic (1% PAL) produces a stronger UV shield than the Archean haze, but the haze shown here cuts out more UVA (320–400 nm) and UVB (280–320 nm) radiation than ozone in all situations.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
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In the paper
“At short wavelengths in direct imaging, haze absorption decreases the planet's brightness; scattering brightens the planet at longer wavelengths.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
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“Thus, we find there is a maximum haze optical thickness—and a minimum temperature from haze-induced cooling—for each atmosphere.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
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In the paper
“This table only includes Case B, but the other cases produce similar results for UV shielding because they have similar optical thicknesses.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
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In the paper
“According to these assumptions, Proterozoic Earth with 0.1% PAL O2 would have received 0.57 W/m2 of UVC at the surface, so in this case, the Archean hazy UV shield was stronger.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Note that even using the conventional habitability threshold of 273 K, Cases A–C have a hazy solution space where Tsurf > 273 K, and Case B stabilizes at Tsurf = 274 K with its thickest haze.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
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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.
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“We find that hazy Archean climates were cold but most likely habitable (Fig. 4).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
- Rests on an assumption: A planet with any nonzero fraction of open ocean is habitable.
A result the paper reports from its own data — 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 the haze-free Case B atmosphere (CH4/CO2 = 0.1), our models calculate the flux of UVC at the surface as about 0.93 W/m2 for a SZA of 60° and 2.62 W/m2 for SZA = 0°.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
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In the paper
“The temperatures of planets A, B, C, and D with ice-albedo feedbacks are 257, 271, 257, and 241 K, a decrease of 3–10 K compared with simulations with the nominal albedo.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
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In the paper
“These features can also be seen in the peaks of the haze imaginary refractive index (Fig. 2).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
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In the paper
“For this world, the CAM produces a global average surface temperature of 287.9 K. Our model produces 285.3 K for this configuration, a difference of 2.6 K.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.2. Comparison with other climate studies
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In the paper
“its buildup in our spectra is not inconsistent with the results of Domagal-Goldman et al. (2011)”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
What the sources say
- Not checked yetcites Domagal-Goldman et al. (2011)
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In the paper
“We achieve the closest match to the Charnay et al. results for a modern continental land mass arrangement: in the GCM, this yields an average albedo of 0.34 and a temperature of 283.7 K, close to our result of 281.1 K for this configuration.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.2. Comparison with other climate studies
What the sources say
- Not checked yetcites Charnay et al.
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In the paper
“This is comparable to, but 5 K warmer than, our global average 1-D result of 282 K.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.2. Comparison with other climate studies
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In the paper
“There is also a very weak haze feature near 3 μm in transit transmission that can be most easily seen in Fig. 10.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
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In the paper
“the other cases produce similar spectra as discussed below.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
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In the paper
“of all the optical constants plotted in Fig. 14, the Khare indices actually produce the closest (although still too low) match to the Hasenkopf Archean real refractive index (n) near 532 nm and produce a reasonable match to the Hasenkopf Archean imaginary refractive index (k), agreeing to within approximately 40% near 532 nm.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
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None of the sources cited for this claim have been checked yet.
In the paper
“Following Wolf and Toon, we find our maximum haze thickness levels off at τ ∼ 5 at 200 nm, which results in a significantly shorter NH3 lifetime of 1 × 104 years, although we did not include NH3 in our photochemical scheme.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.3. Potential for NH3 greenhouse gas shielding
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In the paper
“This difference in temperature is smaller than the difference of using spherical versus fractal particles: our comparison to the Haqq-Misra et al. (2008) study in Section 4.2 shows that particle shape can result in temperature differences >10 K.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
What the sources say
- Not checked yetcites Haqq-Misra et al. (2008)
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
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In the paper
“Note the 1% CH4 Mahjoub imaginary refractive index agrees to within 5% of the Hasenkopf Archean measurement near 532 nm.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
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In the paper
“As we will show, hydrocarbon haze has profound spectral impacts for both reflected light and transit transmission spectra.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction
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In the paper
“Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7–2.6 billion years ago.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > Abstract
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In the paper
“the modeling work of Domagal-Goldman et al. (2008) suggests a longer Mesoarchean to Neoarchean hazy period between 3.2 and 2.7 Ga.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Domagal-Goldman et al., 2008
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In the paper
“S8 is the most important species to rain out S-MIF from the atmosphere; because a more reducing atmosphere enhances the ability of S8 to polymerize, S-MIF is more easily preserved under reducing conditions (Zahnle et al., 2006).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Zahnle et al., 2006
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In the paper
“The S-MIF signal is variable throughout the Archean, and it vanishes completely once O2 builds up to non-negligible levels in the atmosphere after the GOE at 2.5 Ga.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
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In the paper
“Several studies have proposed links between haze and the mass-independent sulfur isotope fractionation signal (S-MIF) (Farquhar et al., 2000) preserved in the geological record before the Great Oxygenation Event (GOE) at about 2.5 Ga”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Farquhar et al., 2000
- Not checked yetcites Domagal-Goldman et al., 2008
- Not checked yetcites Zerkle et al., 2012
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
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In the paper
“The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > Abstract
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In the paper
“Early in Earth's history, an anoxic atmosphere could have supported the formation of an organic haze (Pavlov et al., 2001a; Trainer et al., 2004, 2006; DeWitt et al., 2009; Hasenkopf et al., 2010; Zerkle et al., 2012; Kurzweil et al., 2013; Claire et al., 2014; Izon et al., 2015) that strongly interacted with visible and UV radiation, cooling the planet's climate (Pavlov et al., 2001b; Domagal-Gol”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction
What the sources say
- Not checked yetcites Pavlov et al., 2001a
- Not checked yetcites Trainer et al., 2004, 2006
- Not checked yetcites DeWitt et al., 2009
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In the paper
“The climate model is considered converged when the change in temperature between time steps and change in flux out the top of the atmosphere are sufficiently small (typically on the order of 1 × 10−5).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.1. Coupled photochemical-climate model
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“We have been unable to run the climate model to convergence using the same top-of-atmosphere pressure used for the photochemical model: the photochemical model extends to 100 km, but we have only been able to successfully run the climate model up to about 80 km for our 1 bar atmospheres.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.1. Coupled photochemical-climate model
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Δ36S/Δ33S in Archean sedimentary rocks is generally around −1, but stratigraphic variations in this slope have been observed in the geological record and interpreted as evidence of changes to the S-MIF production mechanism resulting from changes in atmospheric composition (Zerkle et al., 2012; Kurzweil et al., 2013; Izon et al., 2015), suggesting the influence of haze.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Zerkle et al., 2012
- Not checked yetcites Kurzweil et al., 2013
- Not checked yetcites Izon et al., 2015
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
In the paper
“In general, compared to spherical particles, fractal particles produce more extinction in the ultraviolet (UV) but less in the visible and near infrared (NIR).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.1. Coupled photochemical-climate model
What the sources say
- Not checked yetcites Wolf and Toon, 2010
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
In the paper
“they discuss a change in the slope of Δ36S/Δ33S from −1.5 to −0.9 at 2.71 Ga and interpret this to be caused by a decrease in the CH4/CO2 ratio at 2.71 Ga, possibly indicating an organic haze was present for some period of time prior to 2.71 Ga and cleared afterward.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Kurzweil et al., 2013
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The photochemical model is considered converged when redox is conserved and a re-run of the model using last run's output as initial conditions occurs quickly (i.e., <50 time steps).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.1. Coupled photochemical-climate model
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably 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.
None of the sources cited for this claim have been checked yet.
In the paper
“An upper atmosphere haze that decreased tropospheric SO2 photolysis by blocking UV photons and cooled the planet could explain both the glaciation and the decrease in S-MIF.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Domagal-Goldman et al., 2008
- Not checked yetcites Haqq-Misra et al., 2008
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
None of the sources cited for this claim have been checked yet.
In the paper
“In this interpretation, haze-free and reducing atmospheric conditions dominated after 2.71 Ga, with haze reappearing in brief intervals of time as suggested by the Zerkle et al. (2012) and Izon et al. (2015) measurements.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Zerkle et al., 2012
- Not checked yetcites Izon et al., 2015
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“In a real atmosphere, the molecules would be larger before aerosols condense, and back-reactions should occur, so this model may overestimate the rate of aerosol formation.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.1. Coupled photochemical-climate model
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
- The authors state this as an assumption: C4H2 and C5H4 condense directly to haze particles.
In the paper
“Spherical particles in SMART are binned according to log-normal size distributions using the radii mentioned previously and a mode standard deviation of 1.5, which is realistic for an aerosol distribution (Tolfo, 1977).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.2. The SMART model
What the sources say
- Not checked yetcites Tolfo, 1977
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“Note that the version of the model used here can simulate atmospheres ranging from extremely anoxic (pO2 = 10−14) to modern-day O2 levels (Zahnle et al., 2006).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.1. Coupled photochemical-climate model
What the sources say
- Not checked yetcites Zahnle et al., 2006
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“In addition, fractals tend to be more forward scattering in the visible and NIR and more isotropically scattering in the UV compared to equal-mass spherical particles.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.1. Coupled photochemical-climate model
What the sources say
- Not checked yetcites Wolf and Toon, 2010
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
In the paper
“Δ33S typically correlates with enrichments in δ34S and with depletions in δ36S”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Claire et al., 2014
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
In the paper
“In this conceptual model, the end of the cold period typified by low Δ33S may be due to a decrease in the atmospheric CH4/CO2 ratio, which would have cleared any haze present in the atmosphere.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Claire et al., 2014
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
In the paper
“Unlike previous studies of the Archean climate under a haze, we use realistic fractal (rather than spherical) particles, which have different spectral properties and climatic effects.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Wolf and Toon, 2010
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Kurzweil et al. (2013) noted that an increase in magnitude of S-MIF signals after 2.73 Ga (Thomazo et al., 2009) occurred during a prolonged negative shift in δ13Corg, suggesting enhanced biological methane activity at this time.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 1. Introduction > 1.1. Evidence for an Archean haze
What the sources say
- Not checked yetcites Kurzweil et al., 2013
- Not checked yetcites Thomazo et al., 2009
Strength:hedged· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably 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
“However, more recent 3-D studies have shown that Archean Earth can maintain an open ocean fraction of >50% for TGAT ≥ 260 K and an equatorial open ocean belt for TGAT ≥ 248 K (Wolf and Toon, 2013; Charnay et al., 2013).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
What the sources say
- Not checked yetcites Wolf and Toon, 2013
- Not checked yetcites Charnay et al., 2013
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt 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
“These ice-albedo temperatures may be underestimates because once haze forms, deposition of dark hydrocarbons onto ice-covered areas will lower the albedo of the ice. This decreased ice albedo may then melt the ice, reverting parts of the surface back to ocean water.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
In the paper
“This might lead to cooling of the planet or even warming depending on cloud particle size and the altitude—and therefore temperature—of the cloud layer (Goldblatt and Zahnle, 2011).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
What the sources say
- Not checked yetcites Goldblatt and Zahnle, 2011
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
In the paper
“but a recent study of chromium isotopes suggests that the Proterozoic O2 mixing ratio was, at most, 0.1% PAL (Planavsky et al., 2014).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
What the sources say
- Not checked yetcites Planavsky et al., 2014
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
None of the sources cited for this claim have been checked yet.
In the paper
“Later purported hazy periods around 2.7 Ga (Kurzweil et al., 2013; Izon et al., 2015) and between 2.65 and 2.5 Ga (Zerkle et al., 2012) are not associated with glaciations and may be consistent with the thinner-haze solution space of Cases A and C or even the thickest haze solution space of the warmer Case B.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
What the sources say
- Not checked yetcites Kurzweil et al., 2013
- Not checked yetcites Izon et al., 2015
- Not checked yetcites Zerkle et al., 2012
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“DNA damage is most acute in the UVC (λ < 0.28 μm) wavelength range (Pierson et al., 1992; Dillon and Castenholz, 1999), but in the modern atmosphere, UVC is fully blocked by O2 and ozone.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
What the sources say
- Not checked yetcites Pierson et al., 1992
- Not checked yetcites Dillon and Castenholz, 1999
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
In the paper
“Unless otherwise specified, the surface albedo used by the climate model is 0.32. This includes the effect of clouds, which is standard in this 1-D treatment (Kopparapu et al., 2013) and is the albedo that reproduces the average temperature of present-day Earth (288 K) with modern atmospheric conditions.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.3. Model inputs
What the sources say
- Not checked yetcites Kopparapu et al., 2013
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“We set the mixing ratio of O2 at the surface to 1.0 × 10−8, consistent with the Zerkle et al. (2012) study.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.3. Model inputs
What the sources say
- Not checked yetcites Zerkle et al., 2012
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
In the paper
“Furthermore, Abbot et al. (2011) argued that ocean open belts can remain climatologically stable, even if the ice latitude is reduced to 5–15°.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.1. Hazy climates
What the sources say
- Not checked yetcites Abbot et al., 2011
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably 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
“Because methane-producing metabolisms evolved early and Earth's atmosphere was anoxic for about a billion years after the origin of life, pale orange dots may proliferate in the Galaxy if other habitable worlds evolve on similar paths to Earth.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
Tests✓ Asserted: passes✗ Checkable: fails✗ Load-bearing: fails✓ Based: passesProbably 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.
- Rests on an assumption: Methane-producing metabolisms evolved early.
- Rests on an assumption: Earth's atmosphere was anoxic for about a billion years after the origin of life.
In the paper
“Of course, the true cloud distribution on Archean Earth is unknown, and clouds may have had important climatic effects on our early planet (Goldblatt and Zahnle, 2011).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.3. Model inputs
What the sources say
- Not checked yetcites Goldblatt and Zahnle, 2011
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“The solar zenith angles (SZAs) used in the climate and photochemical models were chosen to best represent globally averaged behavior of the physics in each specific model, which Segura et al. (2003) found as SZA = 45° in the photochemical model and SZA = 60° in the climate model. These zenith angles are both tuned to reproduce modern-day Earth's average chemical profiles and climate, respectively.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 2. Models and Methods > 2.3. Model inputs
What the sources say
- Not checked yetcites Segura et al., 2003
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“The impact of these hazes on the biosphere goes beyond temperature reduction: their fractal nature makes them strong absorbers at short wavelengths and therefore a potential shield against damaging UV radiation for the anoxic Archean (Wolf and Toon, 2010), which would have received significantly more UV at the surface than the planet today (Rugheimer et al., 2015).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.2. UV shielding
What the sources say
- Not checked yetcites Wolf and Toon, 2010
- Not checked yetcites Rugheimer et al., 2015
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt 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
“so the occurrence of haze in the habitable zone may be a way to flag interesting planets for careful follow-up study that would search for other indicators of life and quantify the concentration of CH4 and other gases.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.1. Haze and biology
Tests✓ Asserted: passes✗ Checkable: fails✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may be too vague to check against evidence.
In the paper
“which showed much greater C2H6 accumulation on planets orbiting low-mass stars compared to worlds orbiting the Sun.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
What the sources say
- Not checked yetcites Domagal-Goldman et al. (2011)
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“Based on their calculations, Guzmán-Marmolejo et al. (2013) suggested that an atmospheric CH4 concentration greater than 10 ppmv is suggestive of life.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.1. Haze and biology
What the sources say
- Not checked yetcites Guzmán-Marmolejo et al. (2013)
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
In the paper
“The Charnay et al. results for the same atmospheric properties but with an equatorial supercontinent result in the same overall planetary albedo (0.33) but a lower mean temperature of 285 K”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.2. Comparison with other climate studies
What the sources say
- Not checked yetcites Charnay et al.
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt 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
“Our study shows how an Archean haze would have profoundly impacted our planet's environment, habitability, and spectrum.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.1. Haze and biology
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“To consider the spectral effect of haze without contamination from other atmospheric aerosols, the spectra in this section do not include water clouds, even though cloud albedo is implicit in the parameterization of the Atmos model's surface albedo. This makes the albedos of the planets whose spectra are shown in this section darker than those in the Atmos parameterization.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt 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
“Abundant stratospheric water vapor would imply that the planet is in the midst of a moist or runaway greenhouse state and thus is not conventionally habitable.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes? Based: unclearIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Laboratory experiments on organic haze formation have shown that haze-formation chemistry can involve the formation of important prebiotic molecules such as amino acids and nucleotide bases (Khare et al., 1986; McDonald et al., 1994; DeWitt et al., 2009; Hörst et al., 2012; Trainer, 2013)”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.1. Haze and biology
What the sources say
- Not checked yetcites Khare et al., 1986
- Not checked yetcites McDonald et al., 1994
- Not checked yetcites DeWitt et al., 2009
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“We also tested our model results against the Community Atmosphere Model (CAM) GCM nominal Archean atmosphere reported by Wolf and Toon (2013).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.2. Comparison with other climate studies
What the sources say
- Not checked yetcites Wolf and Toon (2013)
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
In the paper
“C2H6 is a greenhouse gas, and its ability to warm in a CH4- and haze-rich atmosphere has been discussed previously (Haqq-Misra et al., 2008).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 3. Results > 3.3. Spectra
What the sources say
- Not checked yetcites Haqq-Misra et al., 2008
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably 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
“Our comparison with these 3-D models suggests the temperatures we present in this work are reasonable but may be underestimates by about 3–5 K.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.2. Comparison with other climate studies
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt 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
“but haze formation is likely considerably more complex and is still not well understood.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.4. Haze formation pathways
Strength:hedged· not yet calibratedTests✓ Asserted: passes✗ Checkable: fails✗ Load-bearing: fails✗ Based: failsProbably 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. It may state two separate claims as one.
In the paper
“The Mahjoub study tested the impact of methane concentration in the gas phase on the resultant hydrocarbon optical properties with gas mixtures containing 1%, 2%, 5%, and 10% CH4 in CH4-N2 mixtures.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
What the sources say
- Not checked yetcites Mahjoub et al.
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably 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
“Following Sagan and Chyba (1997), Wolf and Toon calculated a NH3 atmospheric lifetime of 7 × 107 years for a solar incident flux at a 45° angle assuming τ ∼ 11 at 200 nm.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.3. Potential for NH3 greenhouse gas shielding
What the sources say
- Not checked yetcites Sagan and Chyba (1997)
- Not checked yetcites Wolf and Toon
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
In the paper
“As an example and test of the impact different refractive indices have on our spectra, we examined the sensitivity of our nominal spectra to varied refractive indices measured by Mahjoub et al. (2012).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
What the sources say
- Not checked yetcites Mahjoub et al. (2012)
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“Mass spectrometry of aerosol analogues formed with C/O = 0.1 indicates the formation of carbonyl and carboxyl groups rather than aromatic cycles and long-aliphatic chains, and even suggests the formation of organic acids such as succinic acid (C4H6O4) (DeWitt et al., 2009).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.4. Haze formation pathways
What the sources say
- Not checked yetcites DeWitt et al., 2009
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt 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
“These results suggest that N2 chemical activation could be due to its reaction with the methylidyne (CH) radical formed from CH4 photolysis, to form two radical intermediates, diazomethyl HCNN and its isomer HNCN, which might then react to form HCN and other products.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.4. Haze formation pathways
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“An additional advantage of the Khare refractive indices is that they span an extremely wide wavelength range, ranging from 0.02 to 920 μm, so only one set of optical constants is needed to cover all the wavelengths relevant to photochemistry, climate, and spectra.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
In the paper
“Unfortunately, only one study, that of Hasenkopf et al. (2010), has measured an Archean Earth haze refractive index (as opposed to a titanian haze), and this was only done at a single wavelength (532 nm).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
What the sources say
- Not checked yetcites Hasenkopf et al. (2010)
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Early Earth's atmosphere would have contained negligible O2 but significant amounts of CO2 (e.g., Kasting, 1993; Driese et al., 2011), whereas Titan's atmosphere is extremely reducing (de Kok et al., 2007).”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.4. Haze formation pathways
What the sources say
- Not checked yetcites Kasting, 1993
- Not checked yetcites Driese et al., 2011
- Not checked yetcites de Kok et al., 2007
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“In situ measurements by several instruments on board Cassini have found direct evidence for long hydrocarbons and nitriles chains, benzene (C6H6) and toluene (C6H5CH3), and indirect evidence for polycyclic aromatic hydrocarbons (PAHs) and nitrogen-containing polycyclic aromatic hydrocarbons (PANHs), indicating that these compounds might play a role in the formation of Titan's hazes (Waite et al.,”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.4. Haze formation pathways
What the sources say
- Not checked yetcites Waite et al., 2007
- Not checked yetcites López-Puertas et al., 2013
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“Wolf and Toon (2010) commented on the possibility of a fractal hydrocarbon haze shielding ammonia (NH3) from photolysis, allowing this greenhouse gas to build up in the Archean atmosphere.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.3. Potential for NH3 greenhouse gas shielding
What the sources say
- Not checked yetcites Wolf and Toon (2010)
Strength:hedged· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably 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
“These results bring to light a significant but still unknown mechanism regarding the activation of nitrogen and its inclusion in oxygenated organics, thus providing a new and quantifiable source for these two elements into the early Earth aerosols.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.4. Haze formation pathways
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt 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
“Discovering habitable exoplanets dissimilar to modern Earth will increase the diversity of known habitable environments.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 5. Conclusions
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably not a substantial claim. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Of course this does not account for differences expected in the spectral shape of Archean haze analogues across the UV-visible-IR relative to the titanian haze analogues.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably 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 climatic effects of this haze could have been part of feedbacks between biological CH4 production, atmospheric chemistry, and surface UV radiation.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 5. Conclusions
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“Mahjoub et al. found that refractive indices have a strong dependency on the CH4 concentration over 0.37–1 μm: results indicate that the imaginary index of refraction (k) decreases with increasing CH4 concentration, and the real index of refraction (n) increases with CH4 for the compositions tested.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
What the sources say
- Not checked yetcites Mahjoub et al.
Strength:boosted· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt 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
“Due to the properties of fractal hazes, these particles are relatively transparent at wavelengths longer than approximately the visible range”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✗ Based: failsProbably 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
“The Mahjoub constants do not extend shortward of 0.37 μm, but we should anticipate variation at these shorter wavelengths as well.”
§ The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth > 4. Discussion > 4.5. Optical constants
Strength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✗ Based: failsProbably 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.
The authors state this as an assumption.
Fixed isoprofiles are assumed for CO2 and N2 in the atmospheres considered here.
“Fixed isoprofiles are assumed for CO2 and N2 in the atmospheres considered here.”
The authors state this as an assumption.
C4H2 and C5H4 condense directly to haze particles.
“it is assumed that C4H2 and C5H4 condense directly to haze particles (called HCAER and HCAER2 in Supplementary Table S1).”
The paper relies on this without support.
A planet with any nonzero fraction of open ocean is habitable.
“Since a planet with any nonzero fraction of open ocean is habitable, we regard these updated globally averaged temperatures—all of which are significantly below freezing—to be more realistic habitability thresholds than 273 K.”
The paper relies on this without support.
Methane-producing metabolisms evolved early.
“Because methane-producing metabolisms evolved early and Earth's atmosphere was anoxic for about a billion years after the origin of life, pale orange dots may proliferate in the Galaxy if other habitable worlds evolve on similar paths to Earth.”
The paper relies on this without support.
Earth's atmosphere was anoxic for about a billion years after the origin of life.
“Because methane-producing metabolisms evolved early and Earth's atmosphere was anoxic for about a billion years after the origin of life, pale orange dots may proliferate in the Galaxy if other habitable worlds evolve on similar paths to Earth.”
The paper relies on this without support.
Water vapor clouds have an approximately gray opacity from the visible into the NIR.
“water vapor clouds have an approximately gray opacity from the visible into the NIR.”
The paper relies on this without support.
The tropopause on Earth is at roughly 10 km.
“The tropopause on Earth is at roughly 10 km”
The paper relies on this without support.
Geochemical evidence suggests hazy conditions were not present throughout the entire Archean.
“geochemical evidence suggests hazy conditions were not present throughout the entire Archean”
The paper relies on this without support.
The geochemical constraints on Archean CO2 concentration and geological constraints on surface pressure used in the study are valid.
“consistent with geochemical constraints on CO2 concentration and geological constraints on surface pressure”
The paper relies on this without support.
UVC radiation is harmful to unshielded life.
“may have allowed survival of otherwise unshielded life at the surface of our Archean planet”
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?
The cited source says what the claim attributes to it.
In the citing paper
“A cooling limit exists because as a haze becomes more UV absorbing, it shields CH4 molecules from the photolysis needed for further haze formation.”
From The Archean atmosphere (2020) · cites this paper as [1]
The cited source says what the claim attributes to it.
In the citing paper
“However, whether this shielding actually occurred depends on whether hazes actually existed and on the size and radiative properties of haze particles, which remain uncertain (1, 163).”
From The Archean atmosphere (2020) · cites this paper as [1]
The cited source says what the claim attributes to it.
In the citing paper
“However, too much CH4 relative to CO2 would create the high-altitude organic haze mentioned earlier, which may cool Earth by up to ~20 K (1, 215) by absorbing incoming solar radiation and radiating energy back to space in a so-called “anti-greenhouse effect” (216).”
From The Archean atmosphere (2020) · cites this paper as [1]
The cited source says what the claim attributes to it.
In the citing paper
“Thus, attenuation of sunlight saturates (1, 163).”
From The Archean atmosphere (2020) · cites this paper as [1]
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.
Conflicting criteria for haze-particle growth
MinorThe methods say particles can grow when the coagulation lifetime is longer than the removal lifetime, but the results say growth occurs when the coagulation timescale is shorter than the removal timescale.
“The aerosols can grow when the coagulation lifetime is longer than the lifetime for removal in a layer.”
“In the photochemical model, when the coagulation timescale (τcoag) is shorter than the timescale for removal in an atmospheric layer, the particles can grow.”
Sulfur isotope relationship uses the wrong isotope on its right-hand side
MinorThe text says δ36S is roughly twice δ34S, but the stated mass-dependent relationship makes δ36S proportional to itself instead.
“samples following MDF will have δ33S ∼ 0.515 × δ34S and δ36S ∼ 1.89 × δ36S.”
“the δ36S composition is roughly twice the δ34S amount.”
Example does not give equal log-space bin distances
MinorThe stated binning rule uses distance in log space, but 0.33 μm is not halfway in log space between 0.3 and 0.4 μm. Those bins therefore would not each receive 50% of the mass under the stated rule.
“if Atmos produces a particle of radius 0.33 μm in a layer, the corresponding layer in SMART will include 0.3 and 0.4 μm particles each comprising 50% of the layer's mass.”
“the mass density contributed by the two modes is selected based on the distance in log space of the Atmos particle radius to each neighboring SMART size bin.”
Citations
Cites
Phylogenetic structure of the prokaryotic domain: The primary kingdoms
Woese, C. R., & Fox, G. E. (1977) · Proceedings of the National Academy of Sciences · doi:10.1073/pnas.74.11.5088 · Cited by 4,131 · cited 2×
“5 billion years ago) haze was likely biologically mediated via CH4 produced from methanogenesis, one of the earliest metabolisms (Woese and Fox, 1977; Ueno et al., 2006).”
InfluentialThe formation, properties and impact of secondary organic aerosol: current and emerging issues
Hallquist, M., Wenger, J., Baltensperger, U., Rudich, Y., Simpson, D. M., Claeys, M., Dommen, J., Donahue, N. M., George, C., Goldstein, A. H., et al. (2009) · Atmospheric chemistry and physics · doi:10.5194/acp-9-5155-2009 · Cited by 4,039 · cited 1×
“Since the full chemical scheme that leads to aerosol formation is not well understood despite both laboratory and theoretical studies ( e.g. , Hallquist et al. , 2009; Hicks et al. , 2015), it is assumed that C 4 H 2 and C 5 H 4 condense directly to haze particles (called HCAER and HCAER2 in…”
The HITRAN2012 molecular spectroscopic database
Rothman, L. S., Gordon, I. E., Babikov, Y., Barbe, A., Chris Benner, D., Bernath, P. F., Birk, M., Bizzocchi, L., Boudon, V., Brown, L. R., et al. (2013) · Journal of Quantitative Spectroscopy and Radiative Transfer · doi:10.1016/j.jqsrt.2013.07.002 · Cited by 3,255 · cited 1×
“The Line-by-Line Absorption Coefficients (LBLABC) code, a companion to SMART, creates line-by-line absorption files for input gas mixing ratios and temperature-pressure profiles using HITRAN 2012 line lists (Rothman et al. , 2013).”
Diffuse radiation in the Galaxy
Henyey, L. C., & Greenstein, J. L. (1941) · The Astrophysical Journal · doi:10.1086/144246 · Cited by 2,971 · cited 1×
“Spherical particles use a full Mie phase function, while fractal particles employ a Henyey-Greenstein phase function (Henyey and Greenstein, 1941).”
Atmospheric Influence of Earth's Earliest Sulfur Cycle
Farquhar, J., Bao, H., & Thiemens, M. (2000) · Science · doi:10.1126/science.289.5480.756 · Cited by 1,805 · cited 16×
“Thus, S-MIF is generally regarded as robust evidence for an anoxic Archean atmosphere.”
InfluentialHABITABLE 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 7×
“The version we use here is based directly on that used by Kopparapu et al. (2013).”
InfluentialSelf-citationKasting, J. F. (1993) · Science · doi:10.1126/science.11536547 · Cited by 1,374
A Serpentinite-Hosted Ecosystem: The Lost City Hydrothermal Field
Kelley, D. S., Karson, J. A., Früh-Green, G. L., Yoerger, D. R., Shank, T. M., Butterfield, D. A., Hayes, J. M., Schrenk, M. O., Olson, E. J., Proskurowski, G., et al. (2005) · Science · doi:10.1126/science.1102556 · Cited by 1,288 · cited 1×
“In addition, several abiotic processes including serpentinization (the hydration of ultramafic rocks, mainly olivine and pyroxenes) can form methane (Kelley et al. , 2005; Etiope and Sherwood Lollar, 2013; Guzma´n-Marmolejo et al. , 2013), but the biotic flux of methane to the Archean atmosphere was…”
Photochemistry of the atmosphere of Titan - Comparison between model and observations
Yung, Y. L., Allen, M., & Pinto, J. P. (1984) · The Astrophysical Journal Supplement Series · doi:10.1086/190963 · Cited by 1,081 · cited 2×
“Following the mechanism proposed for the formation of Titan’s hydrocarbon haze (Allen et al. , 1980; Yung et al. , 1984), every model of hydrocarbon haze formation in early Earth’s atmosphere—including ours—has assumed that aerosol formation will occur through the formation of acetylene (C 2 H 2 )…”
Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
Kreidberg, L., Bean, J. L., Désert, J.-M., Benneke, B., Deming, D., Stevenson, K. B., Seager, S., Berta-Thompson, Z. K., Seifahrt, A., & Homeier, D. (2013) · Nature · doi:10.1038/nature12888 · Cited by 938 · cited 2×
“Unlike the hazes that may exist around exoplanets with thick hydrogen-dominated atmospheres (Sing et al., 2011; Knutson et al., 2014; Kreidberg et al., 2014), the Archean (3.”
Influential
Flagged first, then by citations
Research works printed but not linked: 5
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Cited by
Sorted by citations
Items 201–300 of 333
Affholder, A., Mazevet, S., Sauterey, B., Apai, D., & Ferrière, R. (2025) · The Astronomical Journal · doi:10.3847/1538-3881/ada384 · Cited by 7
“…modified versions of models describing the influence on atmospheric composition of ocean and atmospheric chemistry, as well as chemical exchanges between the atmosphere and the crust, the ocean and the atmosphere, and the crust and the ocean (Arney et al. 2016; Krissansen-Totton & Catling 2017).”
CO2 and O2 oxidized 2.7 Ga micrometeorites in two stages suggesting a >32% CO2 atmosphere
Huang, G., Eager-Nash, J. K., Mayne, N. J., Cui, D., Manners, J. C., Hébrard, É., Liu, Z., & Lenton, T. M. (2021) · Precambrian Research · doi:10.1016/j.precamres.2021.106423 · Cited by 6
Mandt, K. E., Luspay‐Kuti, A., Lustig‐Yaeger, J., Felton, R. C., & Domagal-Goldman, S. D. (2022) · The Astrophysical Journal · doi:10.3847/1538-4357/ac59bb · Cited by 6
“Prior knowledge of this chemistry has provided the reaction networks for photochemical models that study the atmosphere of early Earth, which had much less molecular oxygen (O2) than modern Earth does and may have had occasional Titan-like hazes (Arney et al. 2016).”
BackgroundSelf-citationA Correlated‐K Parameterization for O2 Photolysis in the Schumann‐Runge Bands
Ji, A., Tomazzeli, O. G., Palancar, G. G., Chaverot, G., Barker, M., Fernández, R. P., Minschwaner, K. R., & Kasting, J. F. (2024) · Journal of Geophysical Research Atmospheres · doi:10.1029/2023jd040610 · Cited by 7
“D model served as the starting point for several related models, including ATMOS (Arney et al., 2016), EXO‐PRIME 2 (Payne and Kaltenegger, 2024), Photochem (Wogan et al., 2023, 2024; https://github.com/ Nicholaswogan/photochem),aswellasaversionusedbyGermanresearchers(e.g.,Grenfelletal.,2007,2011).”
MethodGilbert-Janizek, S., Meadows, V., & Lustig‐Yaeger, J. (2024) · The Planetary Science Journal · doi:10.3847/psj/ad381e · Cited by 9
“Higher abundances may be due to larger methane surface fl uxes, as may be the case for Archean ( Arney et al. 2016 ) and Proterozoic ( Segura et al. 2003; Young et al. 2024 ) Earth, or longer methane lifetimes in the planetary atmosphere, as may be the case for modern methane fl uxes around K, rather than G, dwarfs ( Ar…”
BackgroundInfluentialSelf-citationExplicit cloud representation in the Atmos 1D climate model for Earth and rocky planet applications
Fauchez, T. J., Arney, G., Kopparapu, R., & Domagal-Goldman, S. (2018) · AIMS Geosciences · doi:10.3934/geosci.2018.4.180 · Cited by 9
Self-citationHarman, C. E., & Domagal-Goldman, S. D. (2018) · Springer eBooks · doi:10.1007/978-3-319-55333-7_71 · Cited by 8
“1) may result in an observable photochemical haze (Haqq-Misra et al. 2008; Harman et al. 2013; Arney et al. 2016), consistent with geochemical evidence for the presence of a haze during several”
InfluentialSelf-citationMak, M. T., Sergeev, D. E., Mayne, N. J., Zamyatina, M., Steinrueck, M. E., Manners, J. C., Hébrard, É., Sing, D. K., & Kohary, K. I. (2025) · Monthly Notices of the Royal Astronomical Society · doi:10.1093/mnras/staf1250 · Cited by 11
Drant, T., Sciamma-O’Brien, E., Jovanović, L., et al. (2025) · Astronomy and Astrophysics · doi:10.1051/0004-6361/202555916 · Cited by 5
What does not kill Gaia makes her stronger: impacts of external perturbations on biosphere evolution
Arthur, R., Nicholson, A., & Mayne, N. (2024) · Monthly notices of the Royal Astronomical Society · doi:10.1093/mnras/stae2003 · Cited by 4
Polarized Signatures of the Earth Through Time: An Outlook for the Habitable Worlds Observatory
Gordon, K. E. G., Karalidi, T., Bott, K., Wogan, N. F., Arney, G., Parenteau, M. N., Kataria, T., & Meadows, V. (2025) · The Astrophysical Journal · doi:10.3847/1538-4357/adc09c · Cited by 14
“…are constant for all models, the particle radii and number density per atmospheric layer of our hazes are based on the Photochem and At-mos models (for more information on these hazes, including their shapes and properties, we refer the reader to Arney et al. (2016); Wogan et al. (2023)).”
InfluentialSelf-citationReed, N. W., Jansen, K. T., Schiffman, Z. R., Tolbert, M. A., & Browne, E. C. (2023) · The Astrophysical Journal Letters · doi:10.3847/2041-8213/acf1a2 · Cited by 5
Christensen, C. M., Reed, N. W., Wing, B. A., McGlynn, S. E., Tolbert, M. A., Browne, E. C., & Surratt, J. D. (2025) · ACS Earth and Space Chemistry · doi:10.1021/acsearthspacechem.4c00314 · Cited by 5
Gebauer, S., Vilović, I., Grenfell, J. L., Wunderlich, F., Schreier, F., & Rauer, H. (2021) · The Astrophysical Journal · doi:10.3847/1538-4357/abd9cc · Cited by 5
Harman, C. E., & Domagal-Goldman, S. D. (2018) · Springer eBooks · doi:10.1007/978-3-319-30648-3_71-1 · Cited by 6
Self-citationEarth: Atmospheric Evolution of a Habitable Planet
Olson, S. L., Schwieterman, E. W., Reinhard, C. T., & Lyons, T. W. (2018) · Springer eBooks · doi:10.1007/978-3-319-30648-3_189-1 · Cited by 5
Self-citationOrganosulfur Aerosols Likely Carried Sulfur MIF Signatures in the Early Earth’s Atmosphere
Oduro, H., Ono, S., Alrasheed, F., & Eldridge, D. L. (2023) · Geochemistry Geophysics Geosystems · doi:10.1029/2022gc010777 · Cited by 5
“These observations may have contributed to the formation of organic aerosols (organic haze) similar to that found in Titan’s atmosphere (Arney et al., 2016; Trainer, 2013).”
BackgroundInfluentialThe Impact of Molecular Oxygen on Anion Composition in a Hazy Archean Earth Atmosphere
Ugelow, M. S., Berry, J. L., Browne, E. C., & Tolbert, M. A. (2020) · Astrobiology · doi:10.1089/ast.2019.2145 · Cited by 6
“In addition to haze potentially being a UV shield to greenhouse gases below the haze, it could have also protected early organisms from the damaging UV light (Arney et al. , 2016).”
InfluentialLatouf, N., Himes, M. D., Mandell, A. M., Moore, M. D., Kofman, V., Villanueva, G. L., & Stark, C. (2024) · The Astronomical Journal · doi:10.3847/1538-3881/ad9729 · Cited by 8
Investigating aerosols as a way to reconcile K2-18 b JWST MIRI and NIRISS/NIRSpec observations
Jaziri, A. Y., & Drant, T. (2025) · Astronomy and Astrophysics · doi:10.1051/0004-6361/202556905 · Cited by 4
The Impact of Extended CO2 Cross Sections on Temperate Anoxic Planet Atmospheres
Broussard, W., Schwieterman, E. W., Sousa‐Silva, C., Sanger-Johnson, G., Ranjan, S., & Vénot, O. (2025) · The Astrophysical Journal · doi:10.3847/1538-4357/adaaf0 · Cited by 4
“This research employs the photochemical model Atmos ( G. Arney et al. 2016, 2018; R. C. Felton et al. 2022; E. W. Schwieterman et al. 2022 ) , the same one-dimensional model as was used by W. Broussard et al. ( 2024 ) .”
InfluentialSelf-citationSeeburger, R., Higgins, P. M., Whiteford, N., & Cockell, C. S. (2023) · Astrobiology · doi:10.1089/ast.2022.0127 · Cited by 4
“This has been assumed to cause the planet to freeze, while Arney et al. (2016) suggested that haze may actually be beneficial to sustaining life on the planet, as the cooling effect is self-limiting, and the haze blocks out much potentially hazardous UV flux.”
BackgroundFisher, T. M., Janin, E., & Walker, S. I. (2025) · The Planetary Science Journal · doi:10.3847/psj/adcc27 · Cited by 5
“The species marked with “ AER ” are atmospheric aerosols. value ) , which is consistent with methanogenesis on Earth during the Archean ( G. Arney et al. 2016 ) .”
InfluentialHumid Evolution of Haze in the Atmosphere of Super-Earths in the Habitable Zone
Maillard, J. F., Carrasco, N., Rüger, C. P., Chatain, A., Schmitz, I., Weisbrod, C. R., Bailly, L., Petit, É., Gautier, T., Mckenna, A. M., et al. (2023) · Astrobiology · doi:10.1089/ast.2022.0021 · Cited by 6
“Thepresence of such hazes is also strongly suspected to have occurred during the Archean eon on early Earth (Kasting et al., 1989; Trainer et al., 2004, 2006; Haqq-Misra et al., 2008; Zerkle et al., 2012; Kurzweil et al., 2013; Izon et al., 2015; Arney et al., 2016).”
Impact of Planetary Parameters on Water Clouds Microphysics
Yang, H., Komacek, T. D., Toon, O. B., Wolf, E. T., Robinson, T. D., Chael, C., & Abbot, D. S. (2024) · The Astrophysical Journal · doi:10.3847/1538-4357/ad3242 · Cited by 4
Self-citationControls of Atmospheric Methane on Early Earth and Inhabited Earth-like Terrestrial Exoplanets
Akahori, A., Watanabe, Y., & Tajika, E. (2024) · The Astrophysical Journal · doi:10.3847/1538-4357/ad47f3 · Cited by 5
Kane, S. R., Bott, K., Gordon, K. E. G., Miles, E. L., Ostberg, C. M., Byrne, P. K., Carone, L., Daylan, T., Muñoz, A. G., Harada, C. K., et al. (2026) · Publications of the Astronomical Society of the Pacific · doi:10.1088/1538-3873/ae417d · Cited by 3
“Thus, quantifying these false-positive biosignatures on hot, cloudy worlds improves the priors used to interpret any future oxygen detections in the HZ (Arney et al. 2016; Mead-ows 2017; Meadows et al. 2018).”
Self-citationAre We the First: Was There Life Before Our Solar System?
Laine, P., & Jheeta, S. (2018) · Elsevier eBooks · doi:10.1016/b978-0-12-811940-2.00014-9 · Cited by 3
The Detectability of Earth’s Biosignatures Across Time
Πάλλη, Ε. (2018) · Springer eBooks · doi:10.1007/978-3-319-55333-7_70 · Cited by 3
“However, Arney et al. 2016 used a coupled climate-photochemical-microphysical simulations to show that hazes can cool the planets surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ=5 at 200 nm) even with the fainter…”
BackgroundExoplanetary Biosignatures for Astrobiology
Grenfell, J. L. (2018) · Advances in astrobiology and biogeophysics · doi:10.1007/978-3-319-96175-0_11 · Cited by 4
Observability of ultraviolet Ni lines in the atmosphere of transiting Earth‐like planets
Young, M. E., Fossati, L., Johnstone, C., Salz, M., Lichtenegger, H., France, K., Lammer, H., & Cubillos, P. E. (2020) · Astronomische Nachrichten · doi:10.1002/asna.202013842 · Cited by 3
“…is a wavelength region that has been largely unexplored for biosignatures in the transmission spectra of terrestrial exoplanets until recently (e.g. Arney et al., 2016; Hu, Seager, & Bains, 2013; Krissansen-Totton et al., 2016; Meadows, 2017; Olson et al., 2018; E. Schwieterman, Reinhard, Olson, &…”
BackgroundStar-Planet Interactions and Habitability: Radiative Effects
Segura, A. (2018) · Springer eBooks · doi:10.1007/978-3-319-30648-3_73-1 · Cited by 3
Ariel – a window to the origin of life on early earth?
Ferus, M., Adam, V., Cassone, G., Civiš, S., Čuba, V., Chatzitheodoridis, E., Drtinová, B., Lefloch, B., Heays, A. N., Jheeta, S., et al. (2020) · Experimental Astronomy · doi:10.1007/s10686-020-09681-w · Cited by 4
Effects of Ultraviolet Radiation on Sub-Neptune Exoplanet Hazes through Laboratory Experiments
Huseby, L., Moran, S. E., Pearson, N., et al. (2025) · The Planetary Science Journal · doi:10.3847/psj/adda4a · Cited by 2
“These hazes vary widely in composition, shape, and size, which in turn changes the optical properties of the haze, leading to variations in opacities sufficient to alter an exoplanet’s spectrum (Arney et al. 2016, 2017; Gavilan et al. 2018; Corrales et al. 2023; He et al. 2024).”
Reassessing the photochemical contribution to Archean Banded Iron Formations
Vergeli, P. C., Romaniello, S. J., Hartnett, H. E., & Anbar, A. D. (2025) · Chemical Geology · doi:10.1016/j.chemgeo.2025.122763 · Cited by 2
Valentine, D. (2025) · doi:10.1093/9780197790885.003.0005 · Cited by 2
Experimental Models on the Prebiotic Formation of Biopolymer Building Blocks
Menor-Salván, C., & Ruiz‐Bermejo, M. (2025) · Astrobiology · doi:10.1177/15311074251365950 · Cited by 5
“…physiology inferred by phylogenetic and molecular clock analysis (Moody et al., 2024); (ii) reconstruction of early Earth ’ s geo-chemistry and mineralogy (Arney et al., 2016; Hazen, 2013; Sahai et al., 2016); (iii) space exploration (McKay, 2014, 2022); and (iv) laboratory models (Camprubi et…”
Gordon, K. E. G., Karalidi, T., Bott, K., et al. (2025) · The Astrophysical Journal · doi:10.3847/1538-4357/ae07df · Cited by 2
“The code assumed an initial surface albedo of 0.65, following the ice-albedo feedback parameterization in Arney et al. (2016) that captures the reflectiveness of both the surface ice and any possible water clouds.”
InfluentialSelf-citationThe Photochemical Plausibility of Warm Exo-Titans Orbiting M Dwarf Stars
Ranjan, S., Wogan, N. F., Glidden, A., Wang, J., Stevenson, K. B., Lewis, N. K., Koskinen, T., Seager, S., Wakeford, H. R., & van der Marel, R. P. (2025) · The Astrophysical Journal Letters · doi:10.3847/2041-8213/ae1026 · Cited by 3
“However, they emphasized that their calculation neglected detailed photochemistry, in particular the possibility of Titan-like haze formation that might inhibit CH 4 photolysis ( G. Arney et al. 2016 ) , increasing the CH 4 lifetime.”
Haqq-Misra, J. D., Kopparapu, R., & Profitiliotis, G. (2025) · The Astrophysical Journal Letters · doi:10.3847/2041-8213/ae23c6 · Cited by 3
“…can draw upon Earth today (e.g., Robinson et al. 2011; Sterzik et al. 2012; Lustig-Yaeger et al. 2023) as well as Earth through time (e.g., Arney et al. 2016, 2018; Schwieterman et al. 2018; Kaltenegger et al. 2020; Tokadjian et al. 2024) to provide examples of atmospheric spectral…”
Is ozone a reliable proxy for molecular oxygen?
Kozakis, T., Mendonça, J. M., Buchhave, L. A., & Lara, L. M. (2025) · Astronomy and Astrophysics · doi:10.1051/0004-6361/202555289 · Cited by 2
Characterizing Exoplanet Habitability
Robinson, T. D. (2017) · Springer eBooks · doi:10.1007/978-3-319-30648-3_67-1 · Cited by 9
Hoehler, T. M., Som, S. M., & Kiang, N. Y.-L. (2018) · Springer eBooks · doi:10.1007/978-3-319-55333-7_74 · Cited by 2
Sharma, A. (2023) · Origins of Life and Evolution of Biospheres · doi:10.1007/s11084-023-09637-y · Cited by 2
Methanol on the rocks: Green rust transformation promotes the oxidation of methanePreprint
Farr, O., Gaudu, N., Danger, G., et al. (2023) · ChemRxiv · doi:10.26434/chemrxiv-2023-4z4n0 · Cited by 2
Turbet, M. (2018) · theses.fr (ABES) · doi:10.70675/6ee472e1z447cz4553zad3ezb856253af054 · Cited by 2
Marcheselli, V. (2025) · doi:10.1093/9780197790885.003.0009 · Cited by 1
Praet, I., & Pitrou, P. (2025) · doi:10.1093/9780197790885.003.0001 · Cited by 1
Buchli, V. (2025) · doi:10.1093/9780197790885.003.0010 · Cited by 1
Messeri, L. R., & Olson, V. (2025) · doi:10.1093/9780197790885.003.0002 · Cited by 1
Praet, I., & Pitrou, P. (2025) · doi:10.1093/9780197790885.001.0001 · Cited by 1
Young, A. V., Robinson, T. D., Krissansen‐Totton, J., Schwieterman, E. W., Arney, G., Lindberg, G. E., & Thomas, C. A. (2025) · The Astrophysical Journal · doi:10.3847/1538-4357/addbd7 · Cited by 1
“Atmos can simulate a wide range of planetary atmospheric environments ( e.g., G. Arney et al. 2016; G. N. Arney et al. 2017; D. J. Teal et al. 2022 ) and calculates self-consistent steady-state profiles of chemical species using 1D plane parallel hydrostatic equilibrium calculations.”
Self-citationHansen, J., Angerhausen, D., Quanz, S. P., Vance, D., Konrad, B. S., Garvin, E. O., Alei, E., Kammerer, J., & Dannert, F. (2025) · The Astrophysical Journal · doi:10.3847/1538-4357/addc6e · Cited by 3
Impacts of Atmospheric Carbon Species and Stellar Type on Climates of Terrestrial Planets
Landry, J., Kurokawa, H., Taki, T., Fujii, Y., Aoki, K., & Genda, H. (2025) · The Planetary Science Journal · doi:10.3847/psj/adf7a1 · Cited by 1
“To calculate the 1D temperature and water vapor profiles of the atmosphere for given sets of partial pressures of carbon species and spectral types of host stars, we used CLIMA, a module of the ATMOS code 1 (Kasting et al. 1984; Arney et al. 2016).”
InfluentialEvolution of Earth's Atmosphere
Jones, C. K., Leung, M., Ebadirad, S., Sneed, E. L., & Lyons, T. W. (2025) · Elsevier eBooks · doi:10.1016/b978-0-323-96026-7.00226-5 · Cited by 2
Kane, S. R., Ernst, R. E., Gillmann, C., Jones, C. K., Lyons, T. W., & Tino, C. (2025) · Elsevier eBooks · doi:10.1016/b978-0-323-95547-8.00005-7 · Cited by 1
Origins of Archean organic matter
Alléon, J., & Summons, R. E. (2025) · Elsevier eBooks · doi:10.1016/b978-0-323-95547-8.00033-1 · Cited by 1
Ebadirad, S., Lyons, T. W., & Fournier, G. P. (2025) · Elsevier eBooks · doi:10.1016/b978-0-323-95547-8.00030-6 · Cited by 3
Limit cycles and the climate history of Mars
Haqq-Misra, J. D. (2026) · Icarus · doi:10.1016/j.icarus.2026.116945 · Cited by 2
Fujii, Y., Angerhausen, D., Matsuo, T., & Wolf, E. T. (2026) · The Astronomical Journal · doi:10.3847/1538-3881/ae367b · Cited by 1
“…self-consistently calculated profiles with radiative transfer and photochemistry under a range of boundary conditions ( L. Kaltenegger & D. Sasselov 2010; L. Kaltenegger et al. 2010; S. Rugheimer et al. 2013, 2015; G. Arney et al. 2016; S. Rugheimer & L. Kaltenegger 2018; M. Braam et al. 2025 ) .”
Self-citationChristensen, C. M., Reed, N. W., Wing, B. A., McGlynn, S. E., Tolbert, M. A., Browne, E. C., & Surratt, J. D. (2026) · ACS Earth and Space Chemistry · doi:10.1021/acsearthspacechem.5c00366 · Cited by 1
On the importance of laboratory experiments for interpreting exoplanet observations
Thompson, M. (2026) · Astrophysics and Space Science · doi:10.1007/s10509-026-04564-6 · Cited by 2
Yu, X., Glein, C. R., Thorngren, D., & Murray, D. F. (2026) · The Astrophysical Journal · doi:10.3847/1538-4357/ae5b6b · Cited by 2
“…are expected to be even more complex ( C. P. McKay et al. 1991; M. G. Tomasko et al. 2008; C. V. Morley et al. 2015; X. Zhang et al. 2015, 2017; G. Arney et al. 2016; P. Lavvas & A. Arfaux 2021 ) and likely to require laboratory experiments to determine their optical properties and assess their…”
Camprubí, E., Pearce, B. K. D., & Preiner, M. (2026) · Astrobiology · doi:10.1177/15311074261454245 · Cited by 1
“This type of atmosphere has also been proposed for early Earth — sometimes referred to as “ the pale orange dot ” model (Arney et al., 2016).”
Benchmarking photolysis rates with Socrates (24.11): species for Earth and exoplanets
Adams, S. M., Manners, J. C., Mayne, N., et al. (2026) · Geoscientific model development · doi:10.5194/gmd-19-5305-2026 · Cited by 1
RETRACTED ARTICLE: Exoplanet Habitability: Potential O2/O3 Biosignatures in the Ultraviolet
Sachkov, M. E., & Shematovich, V. I. (2019) · Solar System Research · doi:10.1134/s003809461905006x · Cited by 1
RetractedBjörn, L. O. (2022) · Biogeosciences · doi:10.5194/bg-19-1013-2022 · Cited by 3
“Their emission of methane to the atmosphere resulted, under the influence of sunlight, in a colored haze of organic compounds, somewhat similar to that now seen on Titan, the largest moon of Saturn (e.g., Arney et al., 2016).”
BackgroundHimes, M. D., Harrington, J., & Baydin, A. G. (2023) · The Planetary Science Journal · doi:10.3847/psj/acc939 · Cited by 1
“…further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. some models can be prohibitive, such as the Atmos photochemical-climate model (Arney et al. 2016) and the free molecular retrieval setup discussed in Chubb & Min (2022).”
MethodThe Climates and Thermal Emission Spectra of Prime Nearby Temperate Rocky Exoplanet Targets
Hammond, T., Komacek, T. D., Kopparapu, R., Fauchez, T. J., Mandell, A. M., Wolf, E. T., Kofman, V., Kane, S. R., Johnson, T. M., Desai, A., et al. (2025) · The Astrophysical Journal · doi:10.3847/1538-4357/adc73b · Cited by 1
“One key constraint regarding the atmospheric composition is that it does not take into account photo-chemistry, especially haze formation in methane-rich atmospheres (Arney et al. 2016, 2017).”
Self-citationGeophysical and geochemical controls on abiotic carbon cycling on Earth-like planetsPreprint
Neveu, M. F., Bartlow, T. L. C., Felton, R. C., Domagal-Goldman, S. D., & Desch, S. J. (2023) · doi:10.22541/essoar.167751627.79222663/v1 · Cited by 2
Self-citationEarliest photic zone niches probed by ancestral microbial rhodopsinsPreprint
Sephus, C. D., Fer, E., Garcia, A. K., et al. (2021) · bioRxiv (Cold Spring Harbor Laboratory) · doi:10.1101/2021.11.18.469010 · Cited by 1
Self-citationYoung, A. V., Robinson, T. D., Krissansen‐Totton, J., et al. (2023) · Research Square · doi:10.21203/rs.3.rs-2335028/v1 · Cited by 1
Self-citationHost Star Driven Photochemistry in Exoplanet Atmospheres
Linsky, J. L. (2019) · Lecture notes in physics · doi:10.1007/978-3-030-11452-7_11
L 98-59: A Benchmark System of Small Planets for Future Atmospheric Characterization
Pidhorodetska, D., Moran, S. E., Schwieterman, E. W., Barclay, T., Fauchez, T. J., Lewis, N. K., Quintana, E. V., Villanueva, G. L., Domagal-Goldman, S. D., Schlieder, J. E., et al. (2021) · The Astronomical Journal · doi:10.3847/1538-3881/ac1171 · Cited by 24
Self-citationDynamics of the Great Oxidation Event from a 3D photochemical-climate model
(2021) · doi:10.5194/cp-2021-150
Self-citationJaziri, Y., Charnay, B., Selsis, F., et al. (2021) · Climate of the past · doi:10.5194/cp-2021-150-rc1
Self-citationJaziri, Y. (2022) · Climate of the past · doi:10.5194/cp-2021-150-ac1
Jaziri, Y., Charnay, B., Selsis, F., et al. (2022) · Climate of the past · doi:10.5194/cp-2021-150-rc2
Self-citationCoker, J. (2019) · Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature · doi:10.3410/f.735646346.793567052
Hoehler, T. M., Som, S. M., & Kiang, N. Y.-L. (2018) · Springer eBooks · doi:10.1007/978-3-319-30648-3_74-1 · Cited by 1
The Detectability of Earth’s Biosignatures Across Time
Πάλλη, Ε. (2018) · Springer eBooks · doi:10.1007/978-3-319-30648-3_70-1
Jaziri, Y. (2022) · Climate of the past · doi:10.5194/cp-2021-150-ac2
Parkinson, C. D., Bougher, S. W., Mills, F. P., Hu, R., Gronoff, G., Brecht, A. S., & Yung, Y. L. (2022) · doi:10.1002/essoar.10511650.1
Fractal Character of Cyanobacteria Thylakoid System Formation
Galitskii, V. V. (2022) · Biology Bulletin Reviews · doi:10.1134/s2079086422050036
“37) and, accordingly, light energy, which was important in the conditions of the Archean Earth with an atmosphere enriched in hydrocarbon components and with a weak young Sun (Arney et al., 2016).”
BackgroundInfluentialThe Fermi Paradox and Astrobiology
Stockton, A. M., Simpson, A., Cable, M. L., Phillips-Lander, C. M., Bennett, C. J., Raj, C. G., Guth-Metzler, R., Pasek, M. A., Pozarycki, C. I., Seaton, K. M., et al. (2023) · Elsevier eBooks · doi:10.1016/b978-0-323-91360-7.00012-4
Parameterizing pressure - temperature profiles of exoplanet atmospheres with neural networksPreprint
Gebhard, T. D., Angerhausen, D., Konrad, B. S., Alei, E., Quanz, S. P., & Schölkopf, B. (2023) · arXiv (Cornell University) · doi:10.3929/ethz-b-000651396
Ranjan, S., Abdelazim, K., Lozano, G. G., et al. (2023) · doi:10.22541/essoar.168500273.36390133/v2
Metz, C. O., Kiang, N. Y.-L., Villanueva, G. L., Parenteau, M. N., & Kofman, V. (2024) · The Planetary Science Journal · doi:10.3847/psj/ad769d
“Organic hazes are formed from photolysis reactions involving methane and may form on Earth-like planets when the atmospheric CH 4 / CO 2 ratio is suf fi ciently high ( M. G. Trainer et al. 2006; G. Arney et al. 2016, 2018 ) .”
Hao, J., Zhang, Z., Li, J., Mondal, J. A., Yu-ke, Z. H. U., Xing, L. I., Hao-tian, G. U. O., Cui, X., Guo, J., Ya-fang, S. O. N. G., et al. (2024) · Bulletin of Mineralogy Petrology and Geochemistry · doi:10.3724/j.issn.1007-2802.20240141 · Cited by 1
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Host Star Driven Photochemistry in Exoplanet Atmospheres
Linsky, J. L. (2025) · Astrophysics and space science library · doi:10.1007/978-3-031-75208-7_11
Star-Planet Interactions and Habitability: Radiative Effects
Segura, A. (2025) · Springer eBooks · doi:10.1007/978-3-319-30648-3_73-2
Blue Vegetation on the Red Planet
Campos, L. A. (2025) · doi:10.1093/9780197790885.003.0003
Helmreich, S. (2025) · doi:10.1093/9780197790885.003.0011
The Restaurant at the End of the World
Parkhurst, A., & Jeevendrampillai, D. (2025) · doi:10.1093/9780197790885.003.0008
Styles of Contemporary Space Exploration
Praet, I. (2025) · doi:10.1093/9780197790885.003.0004
Praet, I., & Pitrou, P. (2025) · doi:10.1093/9780197790885.003.0012
Between a Rock and a Hard Space
Mirmalek, Z. (2025) · doi:10.1093/9780197790885.003.0007 · Cited by 1
Praet, I., & Pitrou, P. (2025) · doi:10.1093/9780197790885.002.0004
Chinigò, D., & Walker, C. (2025) · doi:10.1093/9780197790885.003.0006
Metadata
- Authors
- Arney, G., Domagal-Goldman, S. D., Meadows, V. S., Wolf, E. T., Schwieterman, E., Charnay, B., Claire, M., Hébrard, E., & Trainer, M. G.
- Affiliations
- Goddard Space Flight Center (US)
- University of Washington (US)
- University of Colorado Boulder (US)
- University of California, Riverside (US)
- University of St Andrews (GB)
- NASA Goddard Space Flight Center
- Corresponding author
- Arney, Giada
- ORCID
- Charnay, Benjamin
- Venue
- Astrobiology
- Publisher
- SAGE Publications
- Published
- 2016-11
- Volume
- 16
- Issue
- 11
- Pages
- 873-899
- ISSN
- 1531-1074 (ISSN-L)
- 1557-8070
- PMC
- PMC5148108
- OpenAlex
- W2534050968
- Semantic Scholar
- 62da501fd3e70b940830188582e2e383e75193d3
- Cited by
- 327
- References
- 136
- Citations by year
- 2026: 22 · 2025: 59 · 2024: 28 · 2023: 33 · 2022: 33 · 2021: 30 · 2020: 33 · 2019: 25 · 2018: 45 · 2017: 18 · 2016: 1
- FWCI
- 14.17
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Astrobiology (publishedVersion, cc-by-nc)
- PubMed Central (publishedVersion, cc-by-nc)
- PubMed (publishedVersion)
- Open Research Exeter (University of Exeter) (acceptedVersion)
- arXiv (Cornell University) (submittedVersion)
- HAL (submittedVersion)
- eScholarship (California Digital Library) (submittedVersion, cc-by-nc)
- St Andrews Research Repository (St Andrews Research Repository) (submittedVersion, cc-by-nc)
- arXiv (Cornell University)
- Funders
- Natural Environment Research Council (NE/J022802/2)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Space Science and Extraterrestrial Life
- Physical Sciences › Earth and Planetary Sciences › Space and Planetary Science › Astro and Planetary Science
- Physical Sciences › Earth and Planetary Sciences › Space and Planetary Science › Planetary Science and Exploration
- Keywords
- Archean, atmospheric haze, habitability, faint young Sun, UV protection, biosignatures, methane, self-shielding, exoplanet atmospheres, surface cooling
- MeSH terms
- Atmosphere, Climate, Extraterrestrial Environment, Gases, Models, Theoretical, Particle Size, Spectrophotometry, Ultraviolet, Temperature, Ultraviolet Rays, Water, Earth, Planet, Exobiology
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