¹Scott A. Sandford (>10)
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70221]
¹NASA Ames Research Center, Moffett Field, California, USA

Published by arrangement with John Wiley & Sons

Regolith samples from the carbonaceous asteroid Bennu were stowed and delivered to Earth in the OSIRIS-REx spacecraft’s Sample Return Capsule (SRC). We applied multiple analytical techniques to study the components of the post-flight SRC, with a focus on assessing the conditions and any contaminants to which the Bennu samples were exposed. Examination of the passive temperature sensors placed inside the SRC, in combination with thermal modeling results, indicate that the samples were not heated above the 75°C limit imposed by OSIRIS-REx mission requirements. The sample canister air filter was found to contain Bennu particulates that had escaped from the sample collector, as well as a range of contaminants likely associated with the original filter component materials. No indications of terrestrial soils were found in the filter. Isotopic analyses of organic compounds and noble gases trapped in the filter show values consistent with terrestrial origins, and there are no indications of trapped asteroidal volatiles. Organic compounds found in the flight filter that were not present in a non-flight control filter include aromatic hydrocarbons, alkylated aromatic hydrocarbons, phenolic-related compounds, aliphatic hydrocarbons, and alcohols. The abundances of these organic compounds typically decrease from outer layers of the filter toward the canister interior, suggesting that they are external contaminants. We conclude that the majority of these organic compounds are chemical byproducts associated with outgassing of the SRC heatshield and backshell following the ablation portion of SRC atmospheric entry. Overall, our findings show that the OSIRIS-REx SRC performed excellently in containerizing the asteroidal samples obtained at Bennu, delivering them safely to the ground at the UTTR, and preventing most, though perhaps not all, external contaminants from reaching them. We discuss lessons learned from the flight and recovery of the OSIRIS-REx SRC that can benefit future sample return missions.