Reshaping and ejection processes on rubble-pile asteroids by impacts

TL;DR

This study uses numerical simulations to analyze how impacts affect the shape, material ejection, and deflection of rubble-pile asteroids, with implications for asteroid structure and planetary defense.

Contribution

It provides new insights into how boulder distribution influences impact outcomes on rubble-pile asteroids, relevant for asteroid deflection strategies.

Findings

Post-impact morphology depends on boulder mass-fraction.

Deflection efficiency varies with boulder size and distribution.

Impacts influence asteroid structure and potential for material ejection.

Abstract

Context. Most small asteroids (<50 km in diameter) are the result of the breakup of a larger parent body and are often considered to be rubble-pile objects. Similar structures are expected for the secondaries of small asteroid binaries, including Dimorphos, the smaller component of the 65803 Didymos binary system and the target of NASA's Double Asteroid Redirection Test (DART) and ESA's Hera mission. The DART impact occurs on September 26th, 2022 and it will alter the orbital period of Dimorphos around Didymos. Aims. In this work we assume Dimorphos-like bodies with a rubble-pile structure, and quantify the effects of boulder packing in its interior on the post-impact morphology, degree of shape change and material ejection processes. Methods. We used the Bern SPH shock physics code to numerically model hypervelocity impacts into small, 160 m in diameter rubble-pile asteroids, with a variety of boulder distributions. Results. We find that the post-impact target morphology is most sensitive to the mass-fraction of boulders in the target, while the asteroid deflection efficiency depends on both the mass-fraction of boulders in the target and on the boulder size-distribution close to the impact point. Our results may also have important implications for the structure of small asteroids.