Photo-evaporation of mineral atmosphere from hot rocky exoplanets

Presenter: Yuichi ITO
Until today, over 1000 exoplanets whose radii are less than 2 Earth radii have been discovered. About 50% of those planets have radiative equilibrium temperatures high enough to melt and vaporize rock. Thus, if rocky like CoRoT-7b, they likely have atmospheres composed of rocky materials. There have been no theoretical studies that investigate the escape of the mineral atmosphere in detail, although a hot rocky exoplanet could evolve greatly through loss of planetary mass and atmospheric species if the mineral atmosphere undergoes massive escape. In this study, we constructed an 1-D hydrodynamic model of the highly UV-irradiated, mineral atmosphere, including detailed radiative processes and photo- and thermo-chemistry. Our simulation shows the strong dependence of planetary mass on the mass loss rate of the photo-evaporation. Our results suggest that hot rocky exoplanets of 0.1 Earth mass selectively evaporate through the hydrodynamic escape of the mineral atmospheres, but ones with masses larger than one Earth mass survive.