WATER LOSS FROM TERRESTRIAL PLANETS WITH CO2-RICH ATMOSPHERES

By R. Wordsworth, R. Pierrehumbert. 2013

134 citations recorded by the source corpus.

Water photolysis and hydrogen loss from the upper atmospheres of terrestrial planets is of fundamental importance to climate evolution but remains poorly understood in general. Here we present a range of calculations we performed to study the dependence of water loss rates from terrestrial planets on a range of atmospheric and external parameters. We show that CO2 can only cause significant water loss by increasing surface temperatures over a narrow range of conditions, with cooling of the middle and upper atmosphere acting as a bottleneck on escape in other circumstances. Around G-stars, efficient loss only occurs on planets with intermediate CO2 atmospheric partial pressures (0.1–1 bar) that receive a net flux close to the critical runaway greenhouse limit. Because G-star total luminosity increases with time but X-ray and ultraviolet/ultravoilet luminosity decreases, this places strong limits on water loss for planets like Earth. In contrast, for a CO2-rich early Venus, diffusion limits on water loss are only important if clouds caused strong cooling, implying that scenarios where the planet never had surface liquid water are indeed plausible. Around M-stars, water loss is primarily a function of orbital distance, with planets that absorb less flux than ∼270 W m−2 (global mean) unlikely to lose more than one Earth ocean of H2O over their lifetimes unless they lose all their atmospheric N2/CO2 early on. Because of the variability of H2O delivery during accretion, our results suggest that many “Earth-like” exoplanets in the habitable zone may have ocean-covered surfaces, stable CO2/H2O-rich atmospheres, and high mean surface temperatures.

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/9b269e197475ac3e3e715acbe1b4d599421ef51d

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Atmospheric Science

Citations in the corpus

ABIOTIC OXYGEN-DOMINATED ATMOSPHERES ON TERRESTRIAL HABITABLE ZONE PLANETS (2014, methodology): “…3 shows the variation of atmospheric temperature and H2O molar concentration with atmospheric N2 content calculated using the same methodology as in Wordsworth and Pierrehumbert (2013), for an Earth-like planet at 1 AU around a Sunlike star, assuming an N2−CO2−H2O atmosphere with tropospheric H2O…”
Strange messenger: A new history of hydrogen on Earth, as told by Xenon (2018, background): “FUV radiation does not decay as quickly as XUV, but for present purposes we will ignore this detail, and lump the entire XUV and FUV emission together as a single multiple S of the modern Sun, S (t) ≡ Fxuv/Fxuv .”
The habitability of Proxima Centauri b II. Possible climates and Observability (2016, background): “The amount of water vapor available for escape in the upper atmosphere is thus limited by diffusion (Kasting et al. 1993; Wordsworth & Pierrehumbert 2013).”
ABIOTIC O2 LEVELS ON PLANETS AROUND F, G, K, AND M STARS: POSSIBLE FALSE POSITIVES FOR LIFE? (2015, background): “A good example is a planet interior to the habitable zone that loses its water by way of a runaway or moist greenhouse (Kasting 1988, 1997, 2010; Wordsworth & Pierrehumbert 2013).”
How to Characterize Habitable Worlds and Signs of Life (2017, background): “…that oxygen can build up abiotically under certain geological settings (e.g., Schindler & Kasting 2000, Segura et al. 2007, Selsis et al. 2007, Leger et al. 2011, Hu et al. 2012, Wordsworth & Pierrehumbert 2013, Harman et al. 2015, Tian et al. 2014, Luger & Barnes 2015, Schwieterman et al. 2016).”
Assessing the Habitability of the TRAPPIST-1 System Using a 3D Climate Model (2017, background): “However, their stratospheric H2O volume mixing ratios remain small (∼10−5 at 1 mb) due to efficient cold trapping caused by cooling of the middle and upper atmosphere from high CO2 concentrations (e.g., Wordsworth & Pierrehumbert 2013).”
The Cosmic Shoreline: The Evidence that Escape Determines which Planets Have Atmospheres, and what this May Mean for Proxima Centauri B (2017, background): “This can happen if other gases are scarce (Wordsworth and Pierrehumbert 2013), or the planet could enter a “moist greenhouse” state (Kasting 1988; Kasting et al. 2015; Leconte et al. 2013a; Wolf and Toon 2015).)”
A theoretical framework for volcanic degassing chemistry in a comparative planetology perspective and implications for planetary atmospheres (2014, background): “Why the Earth’s atmosphere pressure is low, hence its surface water-rich, and why this is not the case for Venus remain open questions (Kasting, 1988; Smrekar and Sotin, 2012; Chassefiere et al., 2012; Wordsworth and PierreHumbert, 2013).”