Thermal and Mechanical Consequences of Impact Bombardments to the Silicate Crusts of Terrestrial-type Exoplanets

Post-accretionary impact bombardment is a natural consequence of the planet formation process. Consequently, such late accretion events modulate the initial physical and chemical states of terrestrial planets and their potential to host biospheres. Impact heating can lead to localized, regional, or in extreme cases, wholesale global sterilization of the crust; less intense bombardment can also create hydrothermal oases favorable for life . Here, we generalize the effects of late accretion bombardments to extrasolar planets of several different masses (0.1-10M_E). Thousands of extrasolar terrestrial planets have been discovered, some of which have bulk densities consistent with a rocky composition, and/or orbit within their star’s so-called “habitable zone”. One such planet is Proxima Centauri b, with an estimated mass approximately twice that of Earth. We also model a “mini-Earth”, with a mass 1/10th that of Earth, and a “super-Earth”, with a mass 10 times that of Earth, at the approximate upper limit for transition to a sub-Neptune. We make predictions for lithospheric melting and subsurface habitable volumes.