Extrasolar Planets

Predicted Diversity In Water Content Of Terrestrial Exoplanets Orbiting M Dwarfs

By Keith Cowing
Press Release
September 29, 2022
Predicted Diversity In Water Content Of Terrestrial Exoplanets Orbiting M Dwarfs
Planetary radius, Rp vs. the water content of the “nearly Earth-mass planets” in the habitable zone (HZ-NEMPs) around 0.3M M dwarfs in the case of enriched atmospheres with the primordial-atmospheric water mass fraction XH2O = 0.8. The symbols are colour-coded according to the atmospheric mass relative to the planetary core mass. Atmosphere-free planets are shown by black points. Planets without any water are piled up at Mwater/Mcore = 10−5 for drawing purposes.

Exoplanet surveys around M dwarfs have detected a growing number of exoplanets with Earth-like insolation.

It is expected that some of those planets are rocky planets with the potential for temperate climates favourable to surface liquid water.

However, various models predict that terrestrial planets orbiting in the classical habitable zone around M dwarfs have no water or too much water, suggesting that habitable planets around M dwarfs might be rare. Here we present the results of an updated planetary population synthesis model, which includes the effects of water enrichment in the primordial atmosphere, caused by the oxidation of atmospheric hydrogen by rocky materials from incoming planetesimals and from the magma ocean.

We find that this water production in the primordial atmosphere is found to significantly impact the occurrence of terrestrial rocky aqua planets, yielding ones with diverse water content. We estimate that 5-10% of the planets with a size <1.3R⊕ orbiting early-to-mid M dwarfs have appropriate amounts of seawater for habitability. Such an occurrence rate would be high enough to detect potentially habitable planets by ongoing and near-future M-dwarf planet survey missions.

Tadahiro Kimura, Masahiro Ikoma

Comments: 22 pages, 4 figures. Published in Nature Astronomy (this https URL)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2209.14563 [astro-ph.EP] (or arXiv:2209.14563v1 [astro-ph.EP] for this version)
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Submission history
From: Tadahiro Kimura
[v1] Thu, 29 Sep 2022 06:02:25 UTC (1,773 KB)

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