Abstract EANA2024-71

The magma ocean evolution on the potentially habitable exoplanets TRAPPIST-1 e,f and g begins with a CO2-dominated atmosphere and evolves into an H2O dominated atmosphere. For less than 10 TO initial H2O, the atmosphere desiccates and the evolution ends with a CO2 dominated atmosphere. Otherwise, the final state is
a thick (> 1000 bar) H2O-CO2 atmosphere.

Feedback between H2O and CO2 increases H2O outgassing and reduces CO2 outgassing. Consequently, abiotic O2 build-up and H2O
partitioning in the mantle are increased by 10% to 50%. Eventually, 3% to 6 % of the initial water is retained.
The magma ocean lifetime is only significantly extended with CO2 for TRAPPIST-1 e with 10 TO initial H2O. Here, atmospheric
escape alters the atmosphere’s composition and consequently its radiative properties slowly enough to delay solidification. The pro-
longation of the magma ocean stage results in higher O2 sequestration in the mantle, suppressing atmospheric O2 accumulation, and
culminates in a minimum relative water fraction in the mantle.

Our compositional model adjusted for the measured metallicity of TRAPPIST-1 yields for the dry inner planets (b,c,d) an iron fraction
of 25 wt%. For TRAPPIST-e, this iron fraction would be compatible with a desiccated evolution scenario and a CO2 atmosphere with
surface pressures ě 100 bar. Thus, a comparative study between TRAPPIST-1e and g and the inner planets may yield the most insights
about formation and evolution scenarios by confronting, respectively, a scenario with desiccated evolution to a volatile-rich scenario
to a scenario with volatile-poor formation