A numerical simulation approach to the crater-scaling relationships in low-speed impacts under microgravity

The many small-body exploration missions that have occurred over the last few decades have shown that small solar system objects are covered with granular material of varying depth. These missions have also observed that granular materials are mobilized from the surfaces at speeds on the order of escape speed by different contributing mechanisms. Those result in various outcomes including escape and reimpact. The latter contributes to further impact-driven evolution. Despite the long history of the research in the field of planetary cratering, low-speed impacts have not been studied extensively under gravity levels relevant to small-bodies. Earth-based low-gravity platforms lack the ability to probe microgravity impact physics for a sufficiently long duration to collect meaningful data from experiments. In order to overcome these challenges, this study uses discrete-element method (DEM) simulations to test low-speed cratering at 5-50 cm/s in granular materials in microgravity. The study first presents a procedure for post-processing the raw simulation data to extract the information relevant to the crater-scaling relationships and demonstrates their applicability for crater sizes, ejecta properties and crater formation time. The implications of the results are discussed in the light of results from recent small-body exploration missions.