How Mixed Outgassing Changes The Volatile Distribution In Magma Oceans Around M Dwarf Stars

We investigate the impact of CO₂ on TRAPPIST-1 e, f and g during the magma ocean stage. These potentially habitable rocky planets are currently the most accessible for astronomical observations.

A constraint on the volatile budget during the magma ocean stage is a link to planet formation and also needed to judge their habitability. We perform simulations with 1-100 terrestrial oceans (TO) of H₂O with and without CO₂ and for albedos 0 and 0.75. The CO₂ mass is scaled with initial H2O by a constant factor between 0.1 and 1.

The magma ocean state of rocky planets begins with a CO₂-dominated atmosphere but can evolve into a H2O dominated state, depending on initial conditions. For less than 10 TO initial H₂O, the atmosphere tends to desiccate and the evolution may end with a CO₂ dominated atmosphere. Otherwise, the final state is a thick (>1000 bar) H₂O-CO₂ atmosphere.

Complete atmosphere desiccation with less than 10 TO initial H₂O can be significantly delayed for TRAPPIST-1e and f, when H₂O has to diffuse through a CO₂ atmosphere to reach the upper atmosphere, where XUV photolysis occurs.

As a consequence of CO₂ diffusion-limited water loss, the time of mantle solidification for TRAPPIST-1 e, f, and g can be significantly extended compared to a pure H₂O evolution by up to 40 Myrs for albedo 0.75 and by up to 200 Mrys for albedo 0. The addition of CO₂ further results in a higher water content in the melt during the magma ocean stage.

Our compositional model adjusted for the measured metallicity of TRAPPIST-1 yields for the dry inner planets (b, c, d) an iron fraction of 27 wt-%. For TRAPPIST-1 e, this iron fraction would be compatible with a (partly) desiccated evolution scenario and a CO₂ atmosphere with surface pressures of a few 100 bar. A comparative study between TRAPPIST-1 e and the inner planets may yield the most insights about formation and evolution scenarios.

From CO₂– to H₂O-dominated Atmospheres and Back — How Mixed Outgassing Changes the Volatile Distribution in Magma Oceans Around M dwarf stars

Ludmila Carone, Rory Barnes, Lena Noack, Katy L. Chubb, Patrick Barth, Bertram Bitsch, Alexander Thamm, Alexander Balduin, Rodolfo Garcia, Christiane Helling

Comments: 36 pages, 28 figues, accepted by A&A 9/12/2024
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2412.10192 [astro-ph.EP] (or arXiv:2412.10192v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2412.10192
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Submission history
From: Ludmila Carone
[v1] Fri, 13 Dec 2024 15:03:11 UTC (4,547 KB)
https://arxiv.org/abs/2412.10192
Astrobiology