Extraterrestrial ribose and other sugars in primitive meteorites

1Yoshihiro Furukawa,2,3Yoshito Chikaraishi,3Naohiko Ohkouchi,3Nanako O. Ogawa,4Daniel P. Glavin,4Jason P. Dworkin,1Chiaki Abe,1Tomoki Nakamura
Proceedings of the Nationall Academy of Sciences of the Unites States of America (in Press) Link to Article [https://doi.org/10.1073/pnas.1907169116]
1Department of Earth Science, Tohoku University, 980-8578 Sendai, Japan;
2Institute of Low Temperature Science, Hokkaido University, 060-0819 Sapporo, Japan;
3Biogeochemistry Program, Japan Agency for Marine-Earth Science and Technology, 237-0061 Yokosuka, Japan;
4Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771

Sugars are essential molecules for all terrestrial biota working in many biological processes. Ribose is particularly essential as a building block of RNA, which could have both stored information and catalyzed reactions in primitive life on Earth. Meteorites contain a number of organic compounds including key building blocks of life, i.e., amino acids, nucleobases, and phosphate. An amino acid has also been identified in a cometary sample. However, the presence of extraterrestrial bioimportant sugars remains unclear. We analyzed sugars in 3 carbonaceous chondrites and show evidence of extraterrestrial ribose and other bioessential sugars in primitive meteorites. The 13C-enriched stable carbon isotope compositions (δ13C vs. VPDB) of the detected sugars show that the sugars are of extraterrestrial origin. We also conducted a laboratory simulation experiment of a potential sugar formation reaction in space. The compositions of pentoses in meteorites and the composition of the products of the laboratory simulation suggest that meteoritic sugars were formed by formose-like processes. The mineral compositions of these meteorites further suggest the formation of these sugars both before and after the accretion of their parent asteroids. Meteorites were carriers of prebiotic organic molecules to the early Earth; thus, the detection of extraterrestrial sugars in meteorites establishes the existence of natural geological routes to make and preserve them as well as raising the possibility that extraterrestrial sugars contributed to forming functional biopolymers like RNA on the early Earth or other primitive worlds.

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