Impacts may provide heat for aqueous alteration and organic solid formation on asteroid parent bodies

Abstract

Chemical reactions on asteroid parent bodies, such as aqueous alteration and the formation of organic solids, require a heat source. Radioactive decay in the interiors of these bodies is generally considered the most important heat source, but impact-generated heating is also likely to play a role. Here we present high-velocity impact cratering experiments using thermocouples embedded in the target material to directly measure the spatial and temporal evolution of temperature throughout each impact experiment. We find that the maximum temperature below the crater floor scales with the distance from the impact point, while the duration of temperature rise is scaled by the thermal diffusion time. We use numerical modelling to suggest that, at distances within 2 astronomical units, impacts producing craters of >20\u2009km radius can facilitate aqueous alteration in the material below the crater, while those which produce craters of 1\u2009km radius can support organic solid formation. Impact heating on asteroid parent bodies may be sufficient to facilitate aqueous alteration and the generation of solid organic material in the region below the impact crater floor, according to direct experiments using a two-stage light gas gun.