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Testing key concepts of planetary habitability using observations of nearby rocky exoplanets

Presentation #1011 in the session “Open Engagement Session A”.

Published onMar 17, 2021
Testing key concepts of planetary habitability using observations of nearby rocky exoplanets

The runaway greenhouse transition [1,2], the carbonate-silicate cycle [3,4] and CO2 surface condensation [4,5] are thought to be three of the most essential geophysical/geochemical processes shaping planetary habitability both inside and outside the solar system [4,6]. However, to date, very little is known about the degree of universality of these processes.

At first, I will briefly review recent ideas proposing ways to statistically detect each of these processes at play, using observations of nearby rocky exoplanets [7-12]. These observations are based on the precise measurement of density and/or molecular detections (in particular CO2) on a large number of rocky exoplanets. I will then focus more specifically on observational tests of the runaway greenhouse [9], which we can actually already attempt in the TRAPPIST-1 multiplanetary system using comparative density measurements among the seven planets [13]. Although we do not detect the runaway greenhouse radius inflation effect predicted in [10], we can use atmospheric model predictions to place strong constraints on the water content of TRAPPIST-1 planets [14].

While this work has been mostly carried out with the support of 1-D numerical climate models, I will present very recent results obtained with 3D Global Climate Models [15], taking into account the effect of atmospheric dynamics and clouds.


[1] Kasting (1988), Icarus [2] Goldblatt & Watson (2012), Philosophical Transactions of the Royal Society of London Series A [3] Walker, Hays & Kasting (1981), Journal of Geophysical Research [4] Kasting, Whitmire & Reynolds (1993), Icarus [5] Turbet et al. (2017), Earth and Planetary Science Letters [6] Kopparapu et al. (2013), The Astrophysical Journal [7] Bean, Abbot & Kempton (2017), The Astrophysical Journal Letters [8] Checlair et al. (2019), Astro2020 white paper [9] Turbet et al. (2019), Astronomy & Astrophysics [10] Turbet (2019), Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics [11] Graham & Pierrehumbert (2020), The Astrophysical Journal [12] Lehmer, Catling & Krissansen-Totton (2020), Nature Communications [13] Turbet et al. (2020), Astronomy & Astrophysics [14] Agol et al. (2020), The Planetary Science Journal [15] Turbet et al., in preparation


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