Internal rubble properties of asteroid (101955) BennuOPEN ACCESS 

P. Tricarico, D. J. Scheeres, A. S. French, J. W. McMahon, D. N. Brack, J. M. Leonard, P. Antreasian, S. R. Chesley, D. Farnocchia, Y. Takahashi, E. M. Mazarico, D. Rowlands, D. Highsmith, K. Getzandanner, M. Moreau, C. L. Johnson, L. Philpott, E. B. Bierhaus, K. J. Walsh, O. S. Barnouin, E. E. Palmer, J. R. Weirich, R. W. Gaskell, M. G. Daly, J. A. Seabrook, M. C. Nolan, D. S. Lauretta

accepted to Icarus
Draft 25 August 2021


Update (5 September): Icarus LINK


• The size-frequency distribution of the internal rubble is consistent with what is observed on the surface.
• The estimated bulk density of the rubble is lower than that of representative meteoritic samples, indicating significant micro-porosity.
• The estimated low macro-porosity indicates relatively tight packing of the rubble, possibly due to fragile rubble blocks.”

“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/cm3, corresponding to a 12% macro-porosity. We find the largest rubble particle to be approximately 145 m, whereas the largest void is approximately 10 m. “