Habitable Zones & Global Climate

Potential Long-term Habitable Conditions On Planets With Primordial H-He Atmospheres

By Keith Cowing
astro-ph.EP
June 28, 2022
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Potential Long-term Habitable Conditions On Planets With Primordial H-He Atmospheres
Evolution of the atmosphere structure of 3 planets between 50 Myr and 5 Gyr, without atmosphere loss. All planets have a core mass of 3 M⊕ and an envelope of 10−3 M⊕ and are at 1, 10 and 100 AU separation from their sun-like host-star. The bar in the bottom of the figure shows the state of water for the temperature range of the figure and at a fixed pressure of about 1 kbar, the resulting surface pressure.

Cold super-Earths which retain their primordial, H-He dominated atmosphere could have surfaces that are warm enough to host liquid water. This would be due to the collision induced absorption (CIA) of infra-red light by hydrogen, which increases with pressure.

However, the long-term potential for habitability of such planet has not been explored yet. Here we investigate the duration of this potential exotic habitability by simulating planets of different core masses, envelope masses and semi-major axes. We find that terrestrial and super-Earth planets with masses of ∼1 – 10M⊕ can maintain temperate surface conditions up to 5 – 8 Gyr at radial distances larger than ∼2 AU.

The required envelope masses are ∼10−4M⊕ (which is 2 orders of magnitude more massive than Earth’s), but can be an order of magnitude smaller (when close-in) or larger (when far out). This result suggests that the concept of planetary habitability should be revisited and made more inclusive with respect to the classical definition.

Marit Mol Lous, Ravit Helled, Christoph Mordasini

Comments: 46 pages, 9 figures. Published in Nature Astronomy and available as read-only at this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2206.13859 [astro-ph.EP] (or arXiv:2206.13859v1 [astro-ph.EP] for this version)
Related DOI:
https://doi.org/10.1038/s41550-022-01699-8
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Submission history
From: Marit Mol Lous
[v1] Tue, 28 Jun 2022 09:53:31 UTC (1,251 KB)
https://arxiv.org/abs/2206.13859
Astrobiology, Extrasolar, exoplanet,

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