Bennu is a 490-m diameter, carbonaceous Near-Earth asteroid (Apollo class) classified as Potentially Hazardous due to its small but non-zero long-term Earth-impact probability. NASA’s OSIRIS-REx spacecraft rendezvoused with Bennu in December 2018, collected 121.6 grams of surface material with a TAGSAM device on 20 October 2020, and delivered those samples to Earth on 24 September 2023 — the first U.S. asteroid sample return.

Before sample delivery, OSIRIS-REx revealed that Bennu is an active asteroid that spontaneously ejects particles into temporary orbit, and that its surface is almost entirely covered in loose boulders rather than smooth regolith. Initial 2024 laboratory analysis of the samples has identified abundant hydrated clays and carbon-rich organic molecules.