Extraterrestrial Ribose and other Sugars in Primitive Meteorites
Fifty years after its fall, the Murchison meteorite was shown to contain a high molecular diversity of extraterrestrial organic matter, 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 bio important sugars remained unclear. The results of the analysis of 3 carbonaceous chondrites are show evidence of extraterrestrial ribose along with arabinose, Xylose and Lyxose, 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. A laboratory simulation experiment of a potential sugar formation reaction in space was also conducted. 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 on the early Earth or other primitive worlds.