Ryosuke Sakurai

Abstract Analyzing primitive extraterrestrial samples from asteroids is key to understanding the evolution of the early solar system. The OSIRIS‐REx mission returned samples from the B‐type asteroid Bennu, providing a valuable opportunity to compare them with the Ryugu samples collected by the Hayabusa2 mission. This study examines the representativeness of a fraction of the Bennu samples, which was allocated from NASA to JAXA, by nondestructive characterization of their physical and spectral properties without atmospheric exposure. The reflectance and observed spectral features in the visible‐to‐infrared range of the Bennu sample resemble those from the spectroscopic analysis of different fractions. Additionally, we found differences in the slope of the visible range and band‐center of ~2.7 μm band between the samples and the asteroid surface, which could be explained by the degree of space weathering. A comparative analysis of the Bennu and Ryugu samples revealed spectral similarities, including absorption features indicative of Mg‐rich phyllosilicates, organics, and carbonates, without any evidence of sampling bias or terrestrial alteration. This finding can be used as a benchmark for subsequent Ryugu–Bennu comparative studies.

Abstract NASA's OSIRIS‐REx mission successfully collected and returned ~121.6 g of bulk samples from the B‐type, near‐Earth asteroid (101955) Bennu to Earth in September 2023. Upon returning to Earth, the samples were transported to the NASA Johnson Space Center where most of the samples have been stored and processed. On August 22, 2024, 0.5 wt% of Bennu samples (0.663 g) and a contact pad that collected particles from the surface of Bennu were permanently transferred to JAXA from NASA based on a Memorandum of Understanding and a letter of agreement between the two agencies. Following this, all the Bennu samples have been curated under nitrogen‐purged gloveboxes, called clean chambers in a clean room at the Extraterrestrial Sample Curation Center in Sagamihara. While maintaining the pristinity of samples at the curation, we conduct a series of nondestructive analyses, including near‐infrared spectroscopy within the clean chambers. Bennu curation was conceptualized primarily based on the Hayabusa2 curation, whereas lessons learned from the Hayabusa2 curation were integrated into designing Bennu curation. Here, we describe preparations for the Bennu curation, with an emphasis on the differences from the Hayabusa2 curation.