Regional and Local Topography Effects of Hypervelocity Impacts into Rubble Piles

Kinetic Impactors are one of the most mature technologies available to mitigate a potential asteroid impact with the Earth, but predicting the asteroid’s response to a kinetic impactor requires the use of large-scale numerical simulations. As we learn more about the asteroid population from missions like Haybusa-2 and OSIRIS-REx, it is becoming clear that asteroids are not simple, homogenous bodies but may rather be rubble-pile in nature with boulders littering their surfaces. Predicting how a rubble-pile or boulder field around an impact site alters the ejecta dynamics and cratering can help shed light on the efficiency of a kinetic impactor. Here, we present results of simulated impacts into rubble-piles using the Adaptive Smoothed Particle Hydrodynamics (ASPH) code Spheral. An ellipsoidal rubble-pile asteroid is generated with both small and large boulders and is used as a prototypical asteroid target. Through our simulations, we characterize both the effect that boulders in the local area of the impact have on cratering, as well as how overall regional slopes influence ejecta distributions. We find that local boulder topography can influence crater shapes, and that buried boulders can be exposed and can cause asymmetries and deviations from more typical crater morphologies. However, we find that momentum transfer enhancement is more strongly affected by regional slopes rather than the local boulder topography.