Space rocks that fell to Earth contain ribose, an essential molecule for life’s genetic machinery, and other related sugars. The finding, reported online November 18 in Proceedings of the National Academy of Sciences, lends support to the idea that many of life’s ingredients were delivered to Earth by interplanetary debris.
Many organic molecules have been found in space. Comet Lovejoy, for example, carts around sugar and alcohol, the base ingredients for a decent interplanetary cocktail (SN: 10/23/15). But until now, no one had confirmed an extraterrestrial source for ribose. This molecule forms part of the sugar-phosphate backbone of RNA, molecular workhorses within cells responsible for reading and carrying out instructions encoded in DNA.
Yoshihiro Furukawa, a geochemist at Tohoku University in Sendai, Japan, and colleagues found the ribose, along with several chemically similar sugars, in samples from two meteorites, one collected from Morocco, the other from Australia. By measuring the amounts of carbon-13 in the sugars — a variant of carbon with an extra neutron, which appears more often in organic molecules from space than in their terrestrial counterparts — the team found that the compounds likely originated in space and weren’t picked up on Earth.
The team suspects that the sugars formed from chemical reactions between water and formaldehyde in the meteorites long ago. Previous lab work in a simulated space environment — where ultraviolet light irradiated chilled water, ammonia and methanol — has also shown that ribose could form on interstellar ice grains (SN: 4/7/16). Other similar experiments have done the same for ribose’s chemical cousin deoxyribose, which helps form the backbone of DNA (SN: 12/19/18).