The five letters of the genetic code were on asteroid Ryugu
Samples brought back by Japan's Hayabusa2 mission contain all five bases of DNA and RNA.
The ingredients of life's code were already floating in space billions of years ago. A tiny piece of an asteroid has just confirmed it.
A team of Japanese scientists detected all five nucleobases, the "letters" used to write genetic information in DNA and RNA, in samples from asteroid Ryugu. The study was published in the journal Nature Astronomy.
The samples reached Earth in 2020 aboard the Hayabusa2 mission of the Japanese space agency JAXA, which brought back 5.4 grams of material in total. Under ultra-clean lab conditions to avoid contaminating it, the team extracted the organic molecules with water and hydrochloric acid, purified them and found adenine, guanine, cytosine, thymine and uracil in the two samples analyzed, in similar amounts. In 2023, one of them, uracil, had already been found.
Because Ryugu was collected directly in space, its grains offer one of the cleanest views of the chemistry of the early solar system, free of the contamination meteorites suffer when they fall. The result matches the samples from NASA's asteroid Bennu, where all five bases also turned up in 2025.
Still, each rock has its own mix: the Murchison meteorite is rich in purines, while Bennu and the Orgueil meteorite have more pyrimidines. Ammonia is thought to influence which bases form.
Key facts
- The Hayabusa2 samples totaled 5.4 grams and arrived in 2020.
- The five bases: adenine, guanine, cytosine, thymine and uracil.
- These asteroids preserve material almost unchanged for about 4.5 billion years.
- Published in Nature Astronomy.
The finding strengthens the idea that asteroids may have delivered some of life's ingredients to the early Earth.
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