NUMERICAL MODELING OF THE FORMATION OF LARGE IMPACT CRATERS

Abstract

Herein we present numerical simulations of Chicxulub-scale impact events. We used the three-dimensional version of the SOVA (solid, vapor, air) computer code in hydrodynamic approximation (no strength) to model the initial stage of an oblique impact, and the two-dimensional version of the SALE (simplified arbitrary Lagrangian and Eulerian) code for modeling of the crater collapse. Our estimates of the melt production are slightly higher than previously published estimates. In the case of a 15-km-diameter projectile, the melt zone may reach the crust-mantle boundary, but the mantle is not melted, because of its higher melting entropy. A surprising result is the considerable deviation of the transient cavity volume, obtained in our simulations, from traditional predictions of the experimental scaling law. It seems that highvelocity (>10 km/s) oblique impacts have almost the same cratering efficiency as vertical ones, while laboratory impacts (<5 km/s) follow the experimental scaling law. We estimate the volume of impact melt for a Chicxulub-size crater to be ∼40000 to 50000 km3, for projectile diameters estimated from the experimental scaling law. If all the melt was deposited inside the crater, this volume would be large enough to create a melt pool with a diameter of 100 km and a depth of 6 km. Ejection of melt outside the crater rim decreases the impact-melt body thickness. Implementation of acoustic fluidization into the SALE code allows us to reproduce Chicxulub as a peakring crater.