Asteroid samples from Bennu suggest life's building blocks may be widespread

Samples returned by NASA's OSIRIS‑REx from asteroid Bennu contained at least 14 of the 20 amino acids used by life and 19 other amino acids, and isotopic analysis indicates many of these compounds likely formed in cold, icy regions beyond the early solar system's snow line.

NASA's OSIRIS‑REx mission returned samples from asteroid Bennu in September 2023 that have been analyzed for organic compounds. Researchers identified numerous amino acids in the material, including many used by life on Earth. Isotopic measurements of those amino acids point to formation in a cold, icy environment likely located beyond the early solar system's snow line. The team also reported an unexpected isotopic difference between left- and right-handed forms of glutamic acid, which raises new questions about molecular asymmetry. Known details: - The Bennu sample contained at least 14 of the 20 amino acids used by life on Earth and 19 additional amino acids not used by life. - Isotopic signatures of glycine and other amino acids in Bennu differ from those in the Murchison meteorite and match formation pathways expected in cold, ice-rich regions. - The data suggest these amino acids formed in a region beyond the solar system's snow line or on bodies that originated there. - Left- and right-handed (L- and D-) forms of glutamic acid in the sample were present in equal proportion but showed notably different nitrogen isotope values. - The study and its findings were led by Allison Baczynski and colleagues and were published on Feb. 9 in Proceedings of the National Academy of Sciences. Summary: The analysis expands the types of environments where amino acids—basic ingredients for life—are known to form, showing they can arise in cold, icy regions as well as warmer, water-rich settings. Researchers reported the unexpected isotopic difference between glutamic acid enantiomers and said further study of that anomaly is underway.