All DNA/RNA Nucleobases Are Found On Asteroid Ryugu

Samples from the asteroid Ryugu collected and returned to Earth by the Japanese Hayabusa 2 mission contain all five nitrogenous bases—adenine, guanine, cytosine, thymine, and uracil—that make up nucleic acids, the biomolecules that make life possible on Earth. The study was published today in Nature Astronomy.

All the nitrogenous bases found in DNA and RNA—adenine, guanine, cytosine, thymine, and uracil—are present, in approximately equal proportions, in the asteroid Ryugu . This is according to an analysis of samples brought back to Earth by the Japanese Aerospace Exploration Agency (JAXA) Hayabusa-2 mission , the results of which were published today in the journal Nature Astronomy .

Nitrogenous bases are fundamental components of DNA and RNA, the molecules that form the basis of life on Earth. Their presence in uncontaminated extraterrestrial material—such as samples collected on asteroids and meteorites—is crucial to understanding how these compounds can form in the absence of biological processes and subsequently be transported to Earth by traveling through the Solar System.

Previous analyses of the Ryugu samples had already detected the presence of uracil , while studies of meteorites and samples from the asteroid Bennu had highlighted a greater variety of nitrogenous bases.

In the new study, researchers analyzed two samples from the Ryugu asteroid, identifying all five canonical nucleobases in both: adenine, guanine, cytosine, thymine, and uracil. They then compared these results with the results from the Murchison and Orgueil meteorites , and with samples from the asteroid Bennu.

Significant differences in the nucleobase abundances emerged: while the Ryugu samples contain roughly comparable amounts of purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil), the Murchison meteorite displays a higher abundance of purine bases, while the samples from Bennu and the Orgueil meteorite are relatively richer in pyrimidine bases. According to the authors, these differences reflect the different chemical, environmental, and evolutionary histories of their respective parent bodies.

Despite these differences, however, the discovery of nitrogenous bases in samples from asteroids and meteorites suggests that these compounds are widespread throughout the Solar System and that carbonaceous asteroids may have contributed to the chemical makeup of the early Earth, and thus also to life on it.

Read the article in Nature Astronomy “A complete set of canonical nucleobases in the carbonaceous asteroid (162173) Ryugu“, by Toshiki Koga, Yasuhiro Oba, Yoshinori Takano, Hiroshi Naraoka, Nanako O. Ogawa, Kazunori Sasaki, Hajime Sato, Toshihiro Yoshimura and Naohiko Ohkouchi

Astrobiology, Astrochemistry,