Bennu samples reveal all ingredients needed to build RNA

Scientists analyzing pristine samples returned from asteroid Bennu found ribose and glucose, filling in the last known ingredients needed to build RNA when paired with phosphate and the nucleobases already identified in the same material. NASA said glucose was detected for the first time in an extraterrestrial sample, and the same Bennu extract also contained lyxose, xylose, arabinose and galactose.

The sugar study, published in Nature Geoscience and led by Yoshihiro Furukawa of Tohoku University, used material collected by the OSIRIS-REx mission from the carbon-rich near-Earth asteroid Bennu and returned to Earth for laboratory analysis. Ribose is the five-carbon sugar that forms RNA’s backbone, making its detection especially important for any discussion of how biology’s chemistry may have started.

Earlier Bennu analyses had already found all five canonical nucleobases used by DNA and RNA, along with phosphate. That means Bennu now appears to contain the full chemical set needed to assemble RNA, but the finding is not evidence that life existed on the asteroid. It does, however, strengthen the case that the raw materials for biology were present in the same body of rock and dust.

Researchers also reported that 2-deoxyribose was not detected in the Bennu sample extract. A related analytical study found that the relative abundance pattern of pentose sugars in Bennu is broadly consistent with abiotic formose-type reactions, a chemistry pathway that can build sugars without life.

NASA and the study authors have framed Bennu as a growing inventory of life-related molecules, following earlier reports of amino acids, nucleobases and ammonia in the returned samples. The new sugar results add another piece to that picture and point back to the early Solar System, where prebiotic organic chemistry may have been widespread on asteroid parent bodies and later delivered to early Earth.