Internal rubble properties of asteroid (101955) Bennu

Abstract

Exploration of asteroid (101955) Bennu by the OSIRIS-REx mission has provided an in-depth look at this rubble-pile near-Earth asteroid. In particular, the measured gravity field and the detailed shape model of Bennu indicate significant heterogeneities in its interior structure, compatible with a lower density at its center. Here we combine gravity inversion methods with a statistical rubble-pile model to determine the density and size-frequency distribution (SFD) index of the rubble that constitutes Bennu. The best-fitting models indicate that the SFD of the interior is consistent with that observed on the surface, with a cumulative SFD index of approximately −2.9. The rubble bulk density is approximately 1.35 g/cm 3 , corresponding to a 12% macroporosity. We find the largest rubble particle to be approximately 145 m, whereas the largest void is approximately 10 m.