Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus

“e of the lack of suitable laboratory data on the hot spectrum of HCCH. The massive number of potential absorbers in the atmosphere of these hot objects also have a direct effect on the planetary albedo[50]as well asthecoolingandhence evolution ofthe younghotobjects; comprehensive data is also crucial to model these pro…”

“…atmospheric layer (less than 2x10−6kg H2O / kg AIR) for Case 1 also manifest themselves in Figure 1E and Figure 3A, but they are two orders of magnitude below the Kasting (1988) moist-greenhouse limit (the “Kasting limit”) near each periastron crossing when the eccentricities are at their highest.”

“If Venus did have the same amount of water as Earth, the higher Teff apparently led to a “runaway greenhouse” condition (Kasting, 1988)— positive temperature feedback from greenhouse warming of water vapor winning over all other feedbacks.”

“Detailed models for runaway greenhouse implications for Venus were considered by Pol-lack (1971) and Kasting (1988).”

“High stratospheric H 2 O would also result in increased rates of water loss by way of photodissociation followed by hydrogen escape—a phenomenon sometimes termed a moist greenhouse (Kasting, 1988).”

“(2) When the moon’s global energy189 flux exceeds the critical flux to become a runaway green-190 house (RG), then any liquid surface water reservoirs can191 be lost due to photodissociation into hydrogen and oxy-192 gen in the high atmosphere (Kasting 1988).”

“To obtain OLR in the presence of condensable water vapor, a dry adiabat to moist adiabat to isothermal atmospheric structure is assumed (Kasting 1988).”

“TECTONIC-CLIMATE COUPLING 1837 water loss, either due to photodissociation of H2O in the stratosphere and loss of H to space [Kasting, 1988] or by triggering a full runaway greenhouse [Goldblatt et al., 2013].”

“…surface water, the planet must have an atmosphere with greenhouse gases, which provides the pressure and temperature profile to maintain liquid water and avoid catastrophic water escape (Watson et al. 1981; Kasting 1988; Barnes et al. 2013; Wordsworth and Pierrehumbert 2013; Luger and Barnes 2015).”

“These early stages of planetary formation may entirely determine the habitability of rocky planets (e.g., Kasting, 1988; Zahnle et al., 2007; Hamano et al., 2013; Foley and Driscoll, 2016; Salvador et al., 2017; Driscoll, 2018; Krissansen-Totton et al., 2021a; Miyazaki and Korenaga, 2021, 2022).”

“This is characteristic of a moist greenhouse (Kasting 1988).”

“At this distance, however, the planet, once the liquid ocean starts to form, would presently undergo a H2O runaway greenhouse scenario (Komabayashi 1967; Kasting 1988), rendering it uninhabitable.”

“In any case, oceans may have persisted on early Venus for 600 myr (Kasting, 1988) to as long as several billion years (Grinspoon and Bullock, 2003) and thus the planet possibly provided an early environment sufficiently clement, and for long enough, for an indigenous origin of life (or perhaps…”

“It has been estimated that the carbonate rocks on the Earth hold the equivalent of roughly 60 bars of CO2 [Kasting, 1988], but since a volcanic source has clearly been active on Venus and since the conversion of atmospheric to crustal carbonate occurs much more efficiently in the presence of liquid…”

“…i.e., if tmax , where S is the stellar energy flux at 1 AU and d is the orbital distance in AU), a runaway greenhouse effect starts: (cid:1) all oceans are evaporated, and the surface temperature rises above 1400 K, radiating the energy excess in the near IR and visible range ( e.g., Kasting, 1988).”

“For example, the inner habitable boundary may be defined by critical fluxes, which cause runaway/moisture greenhouse effects (Kasting 1988) while the outer boundary may be constrained by the presence of carbon dioxide in the atmosphere as gas phase, avoiding its condensation (Kasting et al. 1993).”

“Convective adjustment is applied as a common procedure (see, e.g. , Manabe and Wetherald, 1967; Kasting, 1988; Mischna et al. , 2000; Pavlov et al. , 2000) if necessary.”

“…are as follows: the mantle nodules (Wänke et al., 1984) suggest from 1.9 to 3.7 times the mass of the present-day ocean, the magma ocean model (Liu, 1988) 10 times, the Earth accretion model (Ahrens 1989) more than twice, and the measurements of K2O/H2O ratio (Jambon and Zimmerman, 1990)…”

“…& Reynolds (1993) gave the extent of the habitable zone from 0.95 AU to 1.37 AU for our Solar system, with the inner edge being set by the onset of the moist greenhouse process (Kasting 1988) causing loss of water to space, and the outer edge being set by cooling due to the formation of CO2 clouds.”

“This is the type of climate tool that is commonly employed in studies of the “habitable zone” (e.g., Kasting 1988; Kasting et al. 1993; von Paris et al. 2013; Kopparapu et al. 2013, 2014).”

“Kasting (1988) used a radiative-convective climate model to show that the insolation received by early Venus lies close to the runaway greenhouse threshold.”

“It has previously been proposed that significant water may have existed on Venus (e.g. Kasting 1988; Kasting & Pollack 1983), and the consensus view is that any free surface water must have disappeared very early in Venusian history.”

“However, evidence suggests that Venus once hosted large bodies of water [Donahue et al., 1982, Jones and Pickering, 2003], which since boiled away in a runaway greenhouse effect ([Kasting, 1988]), leading to present day surface temperatures of over 400oC.”

“Ever since the pioneering work of Ingersoll (Ingersoll 1969), elaborated on in important ways by Kasting (1988) and Nakajima et al. (1992), the runaway greenhouse phenomenon has played a central role in thinking about planetary evolution.”

“Up-to-date calculations put this limit, which I refer to as the Simpson{Nakajima limit, around 280Wm2 [Goldblatt et al., 2013]. Likewise, the absorption of solar radiation asymptotes to a limit too [Kasting, 1988], as both the levels of absorption and scattering optical depth of unity move high above the surface [Gold…”

“…are likely to undergo rapid escape to space, either due to enhanced loss of water from a warm, wet stratosphere (the “moist greenhouse state”) or due to full ocean evaporation and subsequent escape (the “runaway greenhouse state”) (e.g. Kasting 1988; Kasting et al. 1993; Kopparapu et al. 2013).”

“The inner edge of the habitable zone is set by the moist or runaway greenhouse (Kasting 1988; Nakajima et al. 1992; Goldblatt & Watson 2012), which should not be influenced by the details of the silicate-weathering feedback since the CO2 should have been drawn down to low levels when they occur.”

“Single scattering phase function is assumed to follow the analytical Henyey-Greenstein expression with the asymmetry parameter g given by Kasting (1988).”

“This is required to reassess results obtained assuming fully convective profiles on the divergent fate of Venus and the Earth[3, 4], the circumstellar region where surface liquid water can be stable[6, 9] and the occurrence of surface magma oceans[4, 5, 19, 20, 21].”

“Printed in the Netherlands. astro_eng.tex; 19/03/2022; 19:54; p.1 greenhouse” effect (Kasting, 1988), which will likely spell a definite end to life on our planet.”

“…(17) Hunten et al. 1987), the specific mechanism (s) that caused the current D/H fractionation is (are) uncertain (e.g., Kasting & Pollack 1983; Kasting 1988; Grinspoon 1993; Gillmann et al. 2009; Collinson et al. 2016; Lichtenegger et al. 2016 and reviews by Chassefière et al. 2012; Bullock &…”

“Oxidizing (H2O-CO2-rich) atmospheres and their associated climates have previously been described (Wordsworth and Pierrehumbert, 2013b) but equivalent reducing (H2OCO-H2-rich) atmospheres and climates have not.”

“lso note that for the surface temperatures of ∼500 K, which are expected during the “mush” stage (Lebrun et al., 2013), one can also expect water vapor mixing ratios at the mesopause level near to 1 (Kasting, 1988). For that reason H 2O would have continued to escape effectively, even if there are periods in which ther…”

“10.1029/2020AV000294 4 of 20 AGU Advances OLR in the presence of condensable water vapor, a dry adiabat to moist adiabat to isothermal atmospheric structure is assumed (Kasting, 1988).”

“” Subsequent 1-D radiative-convective modeling work identified what we now term the “runaway greenhouse” (e.g., Komabayasi 1967; Komabayashi 1968; Ingersoll 1969; Pollack 1971; Kasting 1988; Abe and Matsui 1988; Nakajima et al. 1992).”

“When the Sun’s luminosity is 1.4 times its current value, or when its age is 8 Gyr (see Girardi et al. 2000), then depending upon the effects of clouds, a runaway greenhouse may occur and the oceans will be totally vaporized (Kasting 1988).”

“As a comparison, detailed atmospheric models exist for the greenhouse (and antigreenhouse) effect on Titan, Earth, Venus, Mars (Pollack, 1979; Kasting, 1988; McKay et al., 1991; Leconte et al., 2013a); other stellar systems (Selsis et al., 2007); and even for potential free-floating planets…”

“…of 273 K (corresponding to a warm enough climate that generates the water amounts necessary to form the ancient valleys, e.g. Hoke et al., 2011) and integrated a moist adiabat upwards until it intersected the stratospheric temperature profile (see, e.g., Kasting, 1988; Ramirez et al., 2014b).”

“eper than the adiabatic lapse rate, the temperature profile is adjuste d to the wet adiabatic lapse rate. This wet adiabatic lapse rate incorporates either CO2 or H2O as condensing species (see, e.g., Kasting 1988, Kasting 1991or Kasting et al. 1993for a detailed description of convection in the model). The water profil…”

“D climate models (e.g. Kasting 1988; Kasting et al. 1993), the moist greenhouse occurs at a substantially lower stellar flux than a true runaway greenhouse.”

“, 1999], and development of an insulating atmosphere [Matsui and Abe, 1986a, 1986b; Zahnle et al., 1988; Kasting, 1988] all suggest extensive melting during accretion.”

“In the study of solar system planets, there is ongoing debate as to whether or not Venus formed dry (e.g., Lewis 1972; Grinspoon & Lewis 1988) or lost its hydrogen later in its lifetime due to photodissociation of water vapor and hydrodynamic escape (e.g., Kasting 1988).”

“As long as there is permanent liquid water on the surface of a planet, the water cycle becomes active, removing CO2 from the atmosphere by means of weathering reactions and leading to a low level of CO2 (Walker et al. 1981; Kasting & Ackerman 1986; Kasting 1988).”

“In the same way, much more work needs to be done to explore how a planet may go from a temperate to a moist and then a runaway greenhouse state (e.g. Kasting 1988), and 3D GCMs will be needed (e.g. Boukrouche et al. 2021).”

“Thehabitable lifetimes of such planets would likely be much shorter than Earth-like planets (if warm oceanswere present on early Venus, its habitable lifetime would correspond to the lifetime of liquid surface water on the planet – estimates for this range from 600Myr (Kasting 1988) to a few Gyr (Grinspoon & Bullock 2…”

“The massive steam atmosphere then radiatively cools (e.g., Abe & Matsui 1988; Kasting 1988; Zahnle et al. 1988), favoring the production of CH4 and NH3 through thermochemical reactions of the impact-generated H2 with the planet’s initial atmospheric C- and N-bearing molecules (Figure 1, left).”

“Geologic and isotopic evidence suggests that liquid water was present at some point on each of the terrestrial planets of the Solar System (Kasting, 1988; Mojzsis et al., 2001; Squyres et al., 2004).”

“…which plays a key role in Earth’s climateand in the runaway water vapor greenhouse, which is central to the past climate evolution of Venus and also determines the inner edge of the habitable zone (Ingersoll 1969; Kasting 1988; Nakajima et al. 1992; Kasting et al. 1993; Kopparapu et al. 2013).”

“Complete water loss for Earth-equivalent oceans would take a few hundred million years (Kasting, 1988; Kasting et al., 1984; Watson et al., 1981; K. J. Zahnle & Kasting, 1986), depending on extreme ultraviolet (XUV) flux KANE ET AL.”

“Furthermore, liquid water is proposed to have existed on many extraterrestrial bodies at certain periods of their evolutionary history (Kasting, 1988; Baker et al., 2005).”

“…Earth proceeded along different evolutionary paths, as is evident from a comparison of the planets’ satellites (Alemi and Stevenson, 2006), magnetic fields (Nimmo and Stevenson, 2000), tectonics (Solomon et al., 1992), rotational states (Del Genio and Suozzo, 1987), and atmospheres (Kasting, 1988).”

“From an anthropocentric perspective, the CHZ is a region around the host star that would support liquid water on the planetary surface, a requirement for life (Kasting 1988; Kasting et al. 1993); meeting this criterion means a planet is habitable and not that it is necessarily inhabited.”

“This underestimates the water vapor feedback but is still broadly consistent with atmospheres that have not yet entered a runaway greenhouse (e.g., Kasting 1988).”

“A fully realized runaway greenhouse would evaporate the entirety of the oceans into its atmospheres, yielding ∼270 bars of water vapor for every Earth ocean originally present (Kasting 1988), and would have a surface temperature of 1600 K in equilibrium (Goldblatt et al. 2013).”

“estimations. The first assumes the loss of planetary water by a moist greenhouse ( Kasting 1988 ); the second assumes loss of planetary water by a runaway greenhouse; and the third is based on the observation that there was no liquid water on Venus’ surface at least for the last 1 Gyr.”

“Hence, temperature profiles are assumed to be adiabatic, based on Kasting (1988) and Kasting (1991).”

“Kasting (1988) defined that the runaway greenhouse occurs when the critical point of water (~647 K and ~220 bar) is reached on a planet with an Earth-like water inventory.”

“First, the second-to-last column demonstrates the fact that, with the exception of Simulation 8, all of these simulations are well within the moist-greenhouse limit as defined by Kasting (1988); Kasting et al. (1993).”

“The runaway greenhouse state (Kasting, 1988) is assumed on early Venus.”

“In this region, the temperature gradient can be written by the moist adiabat (e.g., Kasting 1988) d ln p d lnT = 1 1 + rsat/ cn + { cv + ` 2 RnT 2 (rsat + ) } rsat + rlcl Rn + `T rsat , (7) where cn, cv and cl are the specific heats of non-condensable molecules, condensable molecules (i.e.,…”