Influence of target strength heterogeneity on impact into an asteroid

The NASA DART mission involves the impact of a kinetic impactor onto the moon Dimorphos of the binary asteroid system Didymos. The mission has significant value in assessing one potential mode of planetary defense, by considering the change in momentum that results from the impact event. Studies of the potential momentum enhancement have been performed using various simulation approaches. Here we examine such an impact event through simulations while considering potential heterogeneity in strength of the target body.

Numerous factors influence the development of the crater and the ejecta evolution during such impacts, including the impact velocity, the impactor shape, the impact obliquity, and the material properties of both the impactor and the target. Typically the impactor size scale is far smaller than the target size scale, and it is likely that the impactor will be completely destroyed at velocities such as that intended in the DART mission. The target material properties could potentially cover a wide range of values, although recent results from Bennu suggest that the local strength can be quite low. The relevant properties of the impacted region on the target include the material density, porosity, and strength. The material strength characteristics of the target model are determined by mechanisms such as fracture and fragmentation of the material, granular flow, and potentially effective plasticity, with some of these mechanisms being irrelevant if the impacted region can be effectively described as a loose collection of grains with low cohesion. The potential competing roles of these material mechanisms are highlighted in this numerical study. If time permits, the influence of gravity on the long-term evolution of the target will also be discussed. It is anticipated that such simulations will help provide insight that will also be useful for future planetary defense missions.