Simulating Hypervelocity Impacts into Rubble Pile Structuresfor Planetary Defense

The Double Asteroid Redirection Test (DART) Mission, NASA’s first planetary defense mission, will be the first fullscale test of a kinetic impactor. In this test, DART will impact into Dimorphos, the secondary of the binary asteroid Didymos, and change its orbit around the primary (Cheng et al. 2018, Rivkin et al. 2021). In preparation for the late September 2022 impact, it is necessary to understand how different aspects of asteroid properties can affect the outcome of the DART impact and quantify those effects. The asteroid rendezvous missions, Hayabusa, Hayabusa2, and Osiris-REx, have given us an unprecedented look at near-Earth asteroids and the diversity of environments that exist on these bodies. Specifically, from the Hayabusa2 and Osiris-REx missions to Ryugu and Bennu, we have seen that some near-Earth asteroids lack significant areas of smooth fine-grained regolith, and are instead are characterized as rubble pile structures made up of larger boulders held together. We know that the deflection efficiency of a kinetic impactor is influenced by the target properties, such as material strength and porosity, with impacts into weaker targets having larger deflection efficiencies. While the prevalence of these rubble pile structures in the broader near-Earth asteroid population is unknown, they could exhibit large variations in material strength on a single body (e.g. very weak regolith and strong boulders). Characterizing how these unique topographies with varying material properties could influence a kinetic impactor deflection is necessary to ensure success in a planetary defense scenario.