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Exospheres and Atmospheric Escape in the TRAPPIST-1 System

Presentation #403.03 in the session “Exoplanets and Systems: Terrestrial Planet Atmospheres 1”.

Published onOct 26, 2020
Exospheres and Atmospheric Escape in the TRAPPIST-1 System

Over the past decade, fast advances both in theoretical and observational studies have significantly improved our understanding of a planet’s habitability. Many of the planets that have been discovered to date are remarkably similar to Earth in terms of their size, mass, and orbital distance to their stars, making them in their planetary system’s habitable zone. Among many factors that make a planet habitable, atmosphere is crucial, especially for keeping the surface warm and safe from intense stellar radiation and extreme space weather for life to form. We examine the loss of neutral atmospheres from seven Earth-like planets in the most nearby planetary system, TRAPPIST-1. We estimate the O loss rate via photochemical mechanisms and characterize the resulting exoplanetary hot atomic corona or exosphere. The study is carried out by utilizing our integrated model framework, which couples our 3D Adaptive Mesh Particle Simulator (AMPS) for planetary exospheres and a 3D multi-species magnetohydrodynamic (MHD) model originally developed for Venus and Mars. The MHD model provides descriptions of the seven planets’ ionospheres to AMPS to simulate their exospheres. All the simulations in this study assume a Venus-like condition for both the ionospheres and thermospheres of the planets, which is also based on an assumption of the absence of a global dipole magnetic field. As many relevant planetary parameters of the TRAPPIST-1 planets are unknown, this study intends to provide one possible interpretation of the atmospheric loss process and sustainability for the seven planets as well as other similar exoplanets in their M-dwarfs’ habitable zones.

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