Astronomy: Nucleic acid precursor detected on Ryugu

Uracil, one of the building blocks necessary to form RNA, and vitamin B3, an important cofactor for metabolism in terrestrial life, have been detected in samples collected from the near-Earth asteroid Ryugu, according to a paper published in Nature Communications. The findings suggest that nucleobases, such as uracil, have an extra-terrestrial origin and were delivered to Earth by carbon-rich meteorites.

The Hayabusa2 spacecraft collected samples from two different landing sites on Ryugu, which are thought to have had different histories, and returned them to Earth in December 2020.

Yasuhiro Oba and colleagues used newly developed small-scale analytical techniques to analyse samples from both landing sites of the asteroid Ryugu. They detected uracil, niacin (vitamin B3), and other organic molecules thought to be important for the synthesis of further complex organic molecules. These molecules may have eventually led to the emergence of the first life on Earth, the authors suggest. They had previously been found by the same research team in meteorites found on Earth, but their detection in pristine samples returned from Ryugu suggests an extra-terrestrial origin.

The authors suggest that these compounds could have been generated by photochemical reactions in interstellar ice, which later led to their incorporation into asteroids as the solar system formed. UV and cosmic radiation may have further altered them over millions of years. The delivery of these compounds to Earth by meteorite impact could have played an important role in the emergence of genetic functions of early life, the authors suggest.