Bennu asteroid samples show amino acids may have formed in icy, radioactive conditions.

Analysis of OSIRIS-REx samples from the 4.6-billion-year-old asteroid Bennu found amino acids and isotopic evidence suggesting some formed in ice exposed to radiation rather than in liquid water; the Penn State-led study compared Bennu results with the Murchison meteorite and found distinct formation signatures.

Samples returned by NASA's OSIRIS-REx mission from the 4.6-billion-year-old asteroid Bennu contain amino acids. New research led by Penn State analyzed those samples and reports isotopic evidence that some amino acids may have formed in ice exposed to radiation in the early outer Solar System. This challenges the prior focus on formation in liquid water through Strecker synthesis. The results were published in the Proceedings of the National Academy of Sciences. Key findings: - NASA's OSIRIS-REx returned dust samples from Bennu in 2023 that included amino acids. - The research team used modified instruments to measure isotopic ratios on low-abundance organics and focused on the amino acid glycine. - Isotopic patterns in Bennu's glycine are consistent with formation in icy, radiation-exposed environments rather than only via Strecker synthesis in liquid water. - A comparison with the Murchison meteorite suggests the Murchison amino acids formed under warmer, water-involved conditions, indicating different parent-body environments. - Two mirror-image forms of glutamic acid found in Bennu showed notably different nitrogen values, an unexpected result the team plans to investigate further. - The research team included scientists from Penn State, the University of Pennsylvania, the American Museum of Natural History, University of Arizona, Rowan University, the Catholic University of America, and NASA Goddard. Summary: The study indicates there are multiple pathways and conditions for amino-acid formation in early solar system materials, broadening the range of environments considered capable of producing life's building blocks. Bennu and Murchison appear to record chemically distinct formation histories. Researchers plan to analyze additional meteorites to determine whether the diversity seen so far is common or limited to specific parent bodies.