All five letters of DNA and RNA turned up in samples from the asteroid Ryugu

Adenine, guanine, cytosine, thymine and uracil, the five nucleobases that spell out DNA and RNA, have all been found in samples from the asteroid Ryugu. A team led by Toshiki Koga reported the result in Nature Astronomy, in a paper called “A complete set of canonical nucleobases in the carbonaceous asteroid (162173) Ryugu.” The paper appeared on March 16, 2026, and the finding circulated again in November through a ScienceDaily republication of an essay from The Conversation.

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The material came from JAXA’s Hayabusa2 mission, which returned samples from the roughly 900-meter asteroid to Earth in December 2020. Both of the two samples analyzed held all five bases, in roughly similar amounts. The author list reads Toshiki Koga, Yasuhiro Oba, Yoshinori Takano, Hiroshi Naraoka, Nanako O. Ogawa, Kazunori Sasaki, Hajime Sato, Toshihiro Yoshimura and Naohiko Ohkouchi.

Two samples, five bases and the extraction method

Per the Nature Portfolio release, all five bases were detected in both Ryugu samples, which were collected by Hayabusa2 at its two landing sites. Earlier analysis of Ryugu material had reported only uracil, a result an international team published in 2023. LiveScience reports that the 2023 preliminary work also found 15 amino acids, and that the new study used more sample material and optimized techniques. The paper is open access at its DOI.

The team extracted organic molecules with water and hydrochloric acid, then purified them for detection, with ultra-clean handling meant to prevent contamination from Earth. Hayabusa2 returned about 5.4 grams of Ryugu material in total, according to the ScienceDaily text. Coverage read for this article does not say how much of that was consumed in the nucleobase analysis, and it does not name the analytical instruments.

Hayabusa2 launched in 2014, touched down on Ryugu in 2019 and returned two dust samples in 2020. Planners had intended to collect three samples but limited collection to two over concerns about risk to the spacecraft, according to The Debrief. Ryugu, discovered in 1999, is shaped like a spinning top and carbonaceous, a class that LiveScience says makes up about 75 percent of asteroids. ScienceDaily adds that the Murchison and Orgueil meteorites and NASA’s Bennu samples serve as the comparison set, because meteorites that fall to Earth risk contamination that pristine returned material avoids.

Purines, pyrimidines and the ammonia correlation

The ScienceDaily text dates the asteroid material to about 4.5 billion years ago, and explains that nucleobases combine with sugars and phosphates to form nucleotides, the building blocks of DNA and RNA. Adenine and guanine are the purines of that set, while cytosine, thymine and uracil are the pyrimidines. Ryugu holds roughly comparable amounts of purines, adenine and guanine, and pyrimidines, cytosine, thymine and uracil. The pattern differs from other carbonaceous material. The Murchison meteorite, which fell in Australia in 1969, is richer in purines, while the Orgueil meteorite, which fell in France in 1864, and NASA’s Bennu samples are richer in pyrimidines. The Debrief calls Ryugu the second carbonaceous asteroid to yield the complete set, after Bennu, which makes the Ryugu result an independent second data point rather than a one-off. Astrobiology.com’s summary of the paper says the authors attribute these differences to the different chemical, environmental and evolutionary histories of the parent bodies.

LiveScience adds that the purine-to-pyrimidine ratio tracks ammonia concentration across Ryugu, Bennu and Orgueil, and that the authors say no known formation mechanism predicts the link, which could point to a previously unrecognized pathway. The Debrief frames the ammonia explanation as possible and conditional on confirmation.

Nucleobases in Ryugu dust are chemistry, not biology

Koga, a biogeochemist at the Japan Agency for Marine-Earth Science and Technology, told AFP that the result does not mean life existed on Ryugu, according to LiveScience. He said it shows that primitive asteroids can produce and preserve molecules relevant to the origin of life. The paper’s authors wrote that the results “reinforce the hypothesis” that carbonaceous asteroids contributed to early Earth’s prebiotic chemistry.

César Menor Salván, an astrobiologist at the University of Alcalá who was not involved in the study, said the results do not suggest that the origin of life took place in space.

Kliti Grice of Curtin University, who wrote the Conversation essay that ScienceDaily republished, notes that meteorites landing on Earth can be contaminated, which is why pristine returned samples such as Ryugu’s are valued. Grice writes that the findings suggest these molecules were widespread in the early Solar System and that asteroids may have delivered such ingredients to early Earth. LiveScience points to the same caution from a separate Ryugu study that found microorganisms, which closely matched Earth bacteria and were most likely contamination after the samples arrived.

The open question is the ammonia link. Ryugu and Bennu are carbonaceous asteroids that JWST observations suggest may share a parent body, and the authors report that no known mechanism predicts why ammonia would set the purine and pyrimidine balance. Whether that correlation reflects real chemistry will need more samples from more asteroids.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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