Issue |
A&A
Volume 679, November 2023
|
|
---|---|---|
Article Number | A126 | |
Number of page(s) | 36 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202347539 | |
Published online | 28 November 2023 |
Water condensation zones around main sequence stars
1
Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École Normale Supérieure, Université PSL, École Polytechnique, Institut Polytechnique de Paris,
75005
Paris,
France
e-mail: mturbet@lmd.jussieu.fr
2
Département d’astronomie de l’Université de Genève,
Chemin Pegasi 51,
1290
Sauverny,
Switzerland
3
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS,
B18N, allée Geoffroy Saint-Hilaire,
33615
Pessac,
France
4
NASA Goddard Space Flight Center,
8800 Greenbelt Road,
Greenbelt, MD
20771,
USA
5
Integrated Space Science and Technology Institute, Department of Physics, American University,
Washington, DC,
USA
6
Centre pour la Vie dans l’Univers, Université de Genève,
Switzerland
7
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris-Cité,
5 place Jules Janssen,
92195
Meudon,
France
8
Université Paris-Saclay, Université Paris-Cité, CEA, CNRS, AIM,
Gif-sur-Yvette
91191,
France
9
Astrobiology Research Unit, University of Liège,
Allée du 6 Août 19,
4000
Liège,
Belgium
10
Sorbonne Universités, UPMC Université Paris 6 et CNRS, UMR 7095, Institut d’Astrophysique de Paris,
98 bis bd Arago,
75014
Paris,
France
Received:
22
July
2023
Accepted:
25
August
2023
Understanding the set of conditions that allow rocky planets to have liquid water on their surface, in the form of lakes, seas, or oceans, is a major scientific step in determining the fraction of planets potentially suitable for the emergence and development of life as we know it on Earth. This effort is also necessary to define and refine what is known as the habitable zone (HZ) in order to guide the search for exoplanets likely to harbor remotely detectable life forms. To date, most numerical climate studies on this topic have focused on the conditions necessary to maintain oceans, but not to form them in the first place. Here we use the three-dimensional Generic Planetary Climate Model, historically known as the LMD generic global climate model, to simulate water-dominated planetary atmospheres around different types of main sequence stars. The simulations are designed to reproduce the conditions of early ocean formation on rocky planets due to the condensation of the primordial water reservoir at the end of the magma ocean phase. We show that the incoming stellar radiation (ISR) required to form oceans by condensation is always drastically lower than that required to vaporize oceans. We introduce a water condensation limit, which lies at significantly lower ISR than the inner edge of the HZ calculated with three-dimensional numerical climate simulations. This difference is due to a behavior change of water clouds, from low-altitude dayside convective clouds to high-altitude nightside stratospheric clouds. Finally, we calculated the transit spectra, emission spectra, and thermal phase curves of TRAPPIST-1b, c, and d with H2O-rich atmospheres, and compared them to CO2 atmospheres and bare rock simulations. We show using these observables that JWST has the capability to probe steam atmospheres on low-mass planets, and could possibly test the existence of nightside water clouds.
Key words: planets and satellites: atmospheres / planets and satellites: terrestrial planets
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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