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Evaporation of a magma ocean in presence of hydrogen & observational implications

Presentation #410.04 in the session Exoplanet Atmospheres: Terrestrial Planets (Oral Presentation)

Published onOct 23, 2023
Evaporation of a magma ocean in presence of hydrogen & observational implications

With the new observational capabilities of space telescopes, it should be possible to better characterize the atmospheres of exoplanets, and provide constraints on interiors. Ultra hot rocky exoplanets, for which the stellar irradiation may maintain a magma ocean at the surface for a long period of time, are candidates for such observations. It has been suggested that the primary hydrogen envelope that is captured during the formation of a planet could be kept in the magma ocean, and therefore we could observe planets with a silicate atmosphere mixed with hydrogen. Our model relies on a Gibbs free-energy minimization to find the vapor composition in equilibrium with the magma ocean (a modified version of the CEA/NASA code (Gordon & McBride (1996)). The vapor composition is then used in an atmospheric model, ATMO (Amundsen et al. 2014), which solves for the pressure-temperature profile by finding the energy flux balance in each layer of the model. Synthetic observations are generated via ATMO. We confirm the thermal inversion of silicate atmospheres and the associated emission features of SiO (Ito et al. 2015, Zilinskas et al. 2022), as well as MgO, Na, K, Fe, which are the strongest candidates for detection. We show that hydrogen will water down the other species, and the thermal inversion is reduced or removed, depending on the temperature of the planet. Cases with a lot of hydrogen will be linked to absorption features of H2O. Surface temperatures will also be affected, and increase for higher content of hydrogen.

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