Craters, boulders and regolith of (101955) Bennu indicative of an old and dynamic surface

Journal article

Small, kilometre-sized near-Earth asteroids are expected to have young and frequently refreshed surfaces for two reasons: collisional disruptions are frequent in the main asteroid belt where they originate, and thermal or tidal processes act on them once they become near-Earth asteroids. Here we present early measurements of numerous large candidate impact craters on near-Earth asteroid (101955) Bennu by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission, which indicate a surface that is between 100 million and 1 billion years old, predating Bennu’s expected duration as a near-Earth asteroid. We also observe many fractured boulders, the morphology of which suggests an influence of impact or thermal processes over a considerable amount of time since the boulders were exposed at the surface. However, the surface also shows signs of more recent mass movement: clusters of boulders at topographic lows, a deficiency of small craters and infill of large craters. The oldest features likely record events from Bennu’s time in the main asteroid belt.

Authors: Walsh, KJ; Jawin, ER; Ballouz, R-L; Barnouin, OS; Bierhaus, EB

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer Nature
• Journal: Nature Geoscience
• Volume: 12
• Issue: 4
• Pages: 242-246
• Publication date: 2019-03-19
• Acceptance date: 2019-02-11
• DOI: 10.1038/s41561-019-0326-6
• EISSN: 1752-0908
• ISSN: 1752-0894
• Keywords: FFR