WORLDTECHJapanese team confirms all five DNA and RNA nucleobases in Ryugu asteroid samples
A team of Japanese scientists reports, in a study published in Nature Astronomy, that all five nucleobases used in DNA and RNA are present in pristine material from the asteroid Ryugu. The finding suggests that key chemical ingredients of genetic material were already present in space billions of years ago.
What the Ryugu analysis found
Nucleobases are nitrogen-containing organic molecules that serve as the lettered units of genetic information in DNA and RNA. The five main ones are adenine and guanine, which are purines, and cytosine, thymine and uracil, which are pyrimidines. When joined with sugars and phosphates, they form nucleotides, the building blocks of genetic material.
The Japanese team reports that every one of the five appears in Ryugu samples returned to Earth in 2020 by the Japan Aerospace Exploration Agency's Hayabusa2 mission, which brought back 5.4 grams of pristine asteroid material. In 2023, an international team had already reported uracil in the same samples.
Because the material is easily contaminated, the researchers worked under ultra-clean laboratory conditions. They drew out the organic molecules using water and hydrochloric acid and then purified them for detection. All five nucleobases were found in the two Ryugu samples the team analysed, in roughly similar amounts.
Earlier finds in other space rocks
The results align with earlier work on space rocks. The Murchison meteorite, which fell in Australia in 1969, and the Orgueil meteorite, which fell in France in 1864, have both yielded a range of organic molecules, including nucleobases. Meteorites that land on Earth can pick up contamination during their journey and landing, which is why pristine samples carry particular weight.
Samples from NASA's mission to the asteroid Bennu also contained all five nucleobases, reported in 2025. Asteroids such as Ryugu, Bennu and the parent body of Orgueil are remnants of the early Solar System and can preserve material largely unchanged for about 4.5 billion years.
Differences in chemical balance
The asteroids differ in their mix of molecules. Murchison is enriched in purines, while Bennu and Orgueil contain more pyrimidines. The researchers note that this balance may be shaped by ammonia, a key molecule that influences which nucleobases can form.
Taken together, the findings indicate that carbon-rich asteroids across the Solar System hold diverse prebiotic chemistry, although the precise mixture varies with each asteroid's chemical environment and history. The study suggests that key components of genetic material may have formed in space and later been delivered to the early Earth.
Open questions
- Which conditions in the early Solar System determined the balance between purines and pyrimidines?
- Did these molecules reach the early Earth in quantities that could have contributed to the origin of life?