Archive | 2021
Thermal consequences of impact bombardments to silicate crusts of terrestrial-type exoplanets
Abstract
Introduction: 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 [e.g., 1-3], or in extreme cases, wholesale global sterilization of the crust [e.g., 4]; less intense bombardment can also create hydrothermal oases favorable for life [e.g, 5]. Here, we generalize the effects of late accretion bombardments to extrasolar planets of several different masses (0.1-10M\uf0c5). 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 [6]. 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 “mini-Neptune” [7]. We make predictions for lithospheric melting and subsurface habitable volumes. Methods: The impact bombardment model [1,2] consists of (i) a stochastic cratering model which populates the surface with craters within specified constraints; (ii) analytical expressions that calculate a temperature field for each crater [e.g., 8,9]; and (iii) a