Impact‐Generated Mixing, Melting and Vaporization of the Early Earth's Crust

Abstract Earth's primary accretion was followed by a protracted flux of interplanetary collisions by leftover planetesimals. The effects of the largest collisions—with bodies possibly exceeding 1,000 km diameter—would have been devastating for terrestrial near‐surface environments. While our understanding of these events is hampered by the lack of terrestrial geological record, modeling provides useful insights on their consequences. In this paper we quantify impact‐generated melting and vaporization of the early Earth via a comprehensive suite of state‐of‐the‐art shock physics numerical models. We consider a wide range of impact scenarios (impactor sizes and velocities) as well as target conditions chosen to encompass early Earth conditions (i.e., geothermal gradients, crustal thickness and composition). We find that impact‐generated melting of the Hadean (4–4.5 Ga) near‐surface was widespread, and that the largest impacts would have effectively dredged‐up mantle melts and redistributed them at the surface. Similarly, large scale vaporization of target and impactor materials would have altered atmospheric chemistry and its redox state well into the Mesoarchean (∼3 Ga). Altogether, these impact‐related processes would have had a profound consequence on the early Earth, and our results will provide a valuable resource for further studies devoted to addressing their environmental consequences.