Interior responses to impacts by different impactor types

Abstract

A number of numerical mantle convection studies from the past two decades have investigated the effects of very large meteorite impacts on mantle dynamics in terrestrial planets, especially Mars. On the grounds that most observed craters seem to have been produced by collisionally evolved bodies, probably main-belt asteroids, the impactors were generally assumed to be rocky and have material parameters similar to those of the target. However, the statistical analysis does not imply that all craters derive from an S-type asteroid, as there is a significant fraction of impactors whose properties differ substantially from those of the target, and the dynamical effects in the interior may be quite different even if the final crater is similar; candidate alternative impactors include C-type asteroids and comets. It is generally not possible to deduce the nature of the impactor from the final crater, because the remnants of the impactor are rarely preserved. We show by analysing scaling laws how different impactors may result in the same final crater on a given planet and investigate some dynamical effects for different impactor types for several bodies in the inner Solar System.