Magma Ocean Evolution Of The TRAPPIST-1 Planets

©NASA

TRAPPIST-1 system

Recent observations of the potentially habitable planets TRAPPIST-1 e, f, and g suggest that they possess large water mass fractions of possibly several tens of wt% of water, even though the host star's activity should drive rapid atmospheric escape.

These processes can photolyze water, generating free oxygen and possibly desiccating the planet. After the planets formed, their mantles were likely completely molten with volatiles dissolving and exsolving from the melt. In order to understand these planets and prepare for future observations, the magma ocean phase of these worlds must be understood. To simulate these planets, we have combined existing models of stellar evolution, atmospheric escape, tidal heating, radiogenic heating, magma ocean cooling, planetary radiation, and water-oxygen-iron geochemistry.

We present magmoc, a versatile magma ocean evolution model, validated against the rocky Super-Earth GJ 1132b and early Earth. We simulate the coupled magma ocean-atmospheric evolution of TRAPPIST-1 e, f, and g for a range of tidal and radiogenic heating rates, as well as initial water contents between 1 and 100 Earth-oceans. We find that TRAPPIST-1 f and g most likely followed the extremely wet scenario with a prolonged magma ocean phase of at least 250 Myr. Planet e probably followed the dry or intermediate track, and may or may not have possessed little water vapour or oxygen in the atmosphere at the time of mantle solidification. For all planets that we investigated, we find that only 3-5% of the initial water will be locked in the mantle after the magma ocean solidified.

Patrick Barth, Ludmila Carone, Rory Barnes, Lena Noack, Paul Mollière, Thomas Henning

Comments: Submitted to Astrobiology, 25 pages, 9 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2008.09599 [astro-ph.EP] (or arXiv:2008.09599v1 [astro-ph.EP] for this version)
Submission history
From: Patrick Barth
[v1] Fri, 21 Aug 2020 17:53:29 UTC (1,414 KB)
https://arxiv.org/abs/2008.09599
Astrobiology

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