Abstract

Hypervelocity impacts of large asteroids and comets play a major role in planetary evolution. For example, the _{200-km Chicxulub impact structure on Earth is widely attributed as the sole or major cause of the mass extinction event that wiped out} 75% of genera, including non-avian dinosaurs, at the end of the Cretaceous 66 Ma. Numerical modelling provides the only means of simulating such large and devastating events, but such models require testing against geophysical and geological constraints. Here I describe recent 2D and 3D numerical simulations of the Chicxulub impact and compare simulation outcomes to geophysical data and the results of IODP Expedition 364: a joint drilling expedition in summer 2016 by the International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP). The drill core sampled the Chicxulub peak ring, an enigmatic ring of mountains within the central crater basin, and shows that the peak ring was formed from uplifted, fractured, shocked, felsic basement rocks. The peak-ring rocks are cross-cut by dikes and shear zones and have an unusually low density and seismic velocity. The models and observations support the idea that the Chicxulub peak ring was formed by the spectacular outward collapse of an overheightened central uplift and provide insight into the impact energy and trajectory, as well as important crustal deformation, fracturing and pore space creation.