WATER LOSS FROM TERRESTRIAL PLANETS WITH CO<sub>2</sub>-RICH ATMOSPHERES

Wordsworth, R.; Pierrehumbert, Raymond T.

doi:10.1088/0004-637x/778/2/154

Cited by 199 publications

(184 citation statements)

References 107 publications

(154 reference statements)

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“…This result underscores the importance of the factors governing the noncondensible inventory on a planet. Wordsworth & Pierrehumbert (2013) found that a highly noncondensible inventory can also inhibit loss of water, and the reasoning in that paper applies to other condensible substances as well.…”

Section: Introductionmentioning

confidence: 76%

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Convection in Condensible-Rich Atmospheres

Ding

Pierrehumbert

2016

ApJ

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Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case-water vapor in Earth's present climate-the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO 2 is thecondensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derivedand used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detailand are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere forbothsteady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.

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Section: Introductionmentioning

confidence: 76%

“…Either effect can keep a nondilute lower atmosphere from being capped by a dilute upper troposphere or dilute stratosphere. The factors governing the diluteness of the stratosphere were discussed in detail in Wordsworth & Pierrehumbert (2013), in connection with loss of volatiles to space.…”

Section: Introductionmentioning

confidence: 99%

Convection in Condensible-Rich Atmospheres

Ding

Pierrehumbert

2016

ApJ

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“…The reason for this is that the tropopause usually acts as an efficient cold trap. The amount of water vapor available for escape in the upper atmosphere is thus limited by diffusion (Kasting et al 1993;Wordsworth & Pierrehumbert 2013).…”

Section: Thin Atmospheres -Implication For Water Lossmentioning

confidence: 99%

The habitability of Proxima Centauri b

Turbet

Leconte

Selsis

et al. 2016

A&A

248

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Radial velocity monitoring has found the signature of a M sin i = 1.3 M ⊕ planet located within the Habitable Zone (HZ) of Proxima Centauri (Anglada-Escudé et al. 2016). Despite a hotter past and an active host star the planet Proxima b could have retained enough volatiles to sustain surface habitability (Ribas et al. 2016). Here we use a 3D Global Climate Model (GCM) to simulate Proxima b's atmosphere and water cycle for its two likely rotation modes (1:1 and 3:2 spin-orbit resonances) while varying the unconstrained surface water inventory and atmospheric greenhouse effect. Any low-obliquity low-eccentricity planet within the HZ of its star should be in one of the climate regimes discussed here. We find that a broad range of atmospheric compositions allow surface liquid water. On a tidally-locked planet with sufficient surface water inventory, liquid water is always present, at least in the substellar region. With a non-synchronous rotation, this requires a minimum greenhouse warming (∼10 mbar of CO 2 and 1 bar of N 2 ). If the planet is dryer, ∼0.5 bar/1.5 bars of CO 2 (respectively for asynchronous/synchronous rotation) suffice to prevent the trapping of any arbitrary small water inventory into polar/nightside ice caps. We produce reflection/emission spectra and phase curves for the simulated climates. We find that atmospheric characterization will be possible by direct imaging with forthcoming large telescopes. The angular separation of 7λ/D at 1 µm (with the E-ELT) and a contrast of ∼10 −7 will enable high-resolution spectroscopy and the search for molecular signatures, including H 2 O, O 2 , and CO 2 . The observation of thermal phase curves can be attempted with JWST, thanks to a contrast of 2 × 10 −5 at 10 µm. Proxima b will also be an exceptional target for future IR interferometers. Within a decade it will be possible to image Proxima b and possibly determine whether this exoplanet's surface is habitable.

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“…Tian (2009) showed that in highly irradiated super-Earth atmospheres dissociation of CO 2 can lead to both carbon and oxygen loss, with carbon escaping more rapidly due to its lower atomic weight. Wordsworth & Pierrehumbert (2013) showed that water loss from CO 2 -rich atmospheres can still be substantial, especially for planets that receive more insolation than the present-day Earth, such as GJ 1132b. While CO 2 is effective at cooling the upper atmosphere, which can hinder loss in more temperate planets, a back-of-the-envelope calculation suggests that the degree of cooling from the CO 2 15 μm non-LTE emission would still be far lower than the XUV flux received by GJ 1132b, at least for the first gigayear.…”

Section: Effect Of Comentioning

confidence: 99%

PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

Schaefer

Wordsworth²,

Berta-Thompson

et al. 2016

ApJ

174

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GJ 1132b is a nearby Earth-sized exoplanet transiting an M dwarf, and is among the most highly characterizable small exoplanets currently known. In this paper,we study the interaction of a magma ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the amount of O 2 that can build up in the atmosphere as a result of hydrogen dissociation and loss. We find that the magma ocean absorbs at most ∼10% of the O 2 produced, whereas more than 90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132b from our simulations is a tenuous atmosphere dominated by O 2 , though, for very large initial water abundances,atmospheres with several thousands of bars of O 2 are possible. A substantial steam envelope would indicate either the existence of an earlier H 2 envelope or low XUV flux over the system's lifetime. A steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132b. Further modeling is needed to study the evolution of CO 2 or N 2 -rich atmospheres on GJ 1132b.

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WATER LOSS FROM TERRESTRIAL PLANETS WITH CO₂-RICH ATMOSPHERES

Cited by 199 publications

References 107 publications

Convection in Condensible-Rich Atmospheres

Convection in Condensible-Rich Atmospheres

The habitability of Proxima Centauri b

PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

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WATER LOSS FROM TERRESTRIAL PLANETS WITH CO2-RICH ATMOSPHERES

Cited by 199 publications

References 107 publications

Convection in Condensible-Rich Atmospheres

Convection in Condensible-Rich Atmospheres

The habitability of Proxima Centauri b

PREDICTIONS OF THE ATMOSPHERIC COMPOSITION OF GJ 1132b

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Resources

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WATER LOSS FROM TERRESTRIAL PLANETS WITH CO₂-RICH ATMOSPHERES