Statistical Analysis of Near-surface Structure and Material Properties on Momentum Transfer in Rubble Pile Targets Impacted by Kinetic Impactors

Abstract Rubble pile asteroids consist of reassembled fragments of once larger monolithic asteroid parent bodies. Recent spacecraft missions to asteroids like Itokawa, Ryugu, Bennu, and Dimorphos suggest that rubble pile asteroids are common in the asteroid population, and rubble piles could be a likely structure among potentially hazardous objects. Therefore, it is important to understand the response of rubble pile targets to kinetic impacts for potential future deflection needs. The recent Double Asteroid Redirection Test (DART) mission motivates an investigation of kinetic impacts into rubble pile targets to understand their effects on deflection. Here, we simulate kinetic impacts into Dimorphos-sized asteroid targets to understand the effect of the impact site structure on the deflection efficiency of relevant sizes for planetary defense. We perform 52 two-dimensional simulations where we vary the impact site structure of the impact site, the target porosity, and the material behavior/strength model to understand their relative effects on crater size and the momentum enhancement factor ( β ). We find that the effects of the impact site on both crater size and β are greatest for impacts into weaker targets, where impact sites rich in matrix material result in statistically larger craters and higher β s compared to impact sites rich in boulder material. Further, impact site structures that promote increased boulder ejection result in larger β values. These results provide important intuition to understand the DART impact and to extrapolate results to future potential missions.