Near-zero cohesion and loose packing of Bennu's near subsurface revealed by spacecraft contact

Kevin J. Walsh, Ronald Louis Ballouz, Erica R. Jawin, Chrysa Avdellidou, Olivier S. Barnouin, Carina A. Bennett, Edward B. Bierhaus, Brent J. Bos, Saverio Cambioni, Harold C. Connolly, Marco Delbo, Daniella N. DellaGiustina, Joseph DeMartini, Joshua P. Emery, Dathon R. Golish, Patrick C. Haas, Carl W. Hergenrother, Huikang Ma, Patrick Michel, Michael C. NolanRyan Olds, Benjamin Rozitis, Derek C. Richardson, Bashar Rizk, Andrew J. Ryan, Paul Sánchez, Daniel J. Scheeres, Stephen R. Schwartz, Sanford H. Selznick, Yun Zhang, Dante S. Lauretta

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

When the OSIRIS-REx spacecraft pressed its sample collection mechanism into the surface of Bennu, it provided a direct test of the poorly understood near-subsurface physical properties of rubble-pile asteroids, which consist of rock fragments at rest in microgravity. Here, we find that the forces measured by the spacecraft are best modeled as a granular bed with near-zero cohesion that is half as dense as the bulk asteroid. The low gravity of a small rubble-pile asteroid such as Bennu effectively weakens its near subsurface by not compressing the upper layers, thereby minimizing the influence of interparticle cohesion on surface geology. The underdensity and weak near subsurface should be global properties of Bennu and not localized to the contact point.

Original languageEnglish (US)
Article numberabm6229
JournalScience Advances
Volume8
Issue number27
DOIs
StatePublished - Jul 2022

ASJC Scopus subject areas

  • General

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