A new study has detected all five major nucleobases—the molecular “letters” used by DNA and RNA—in pristine samples collected from asteroid Ryugu. The findings strengthen the possibility that essential components of genetic material formed in space and were later delivered to the early Earth by asteroids.
The Ryugu particles were returned to Earth in 2020 by Hayabusa2, a mission led by the Japan Aerospace Exploration Agency (JAXA). The samples were brought back from space after the spacecraft collected them directly from the asteroid.
In 2023, an international team reported finding uracil, one of the five nucleobases, in Ryugu material. In the new study, published in Nature Astronomy, Japanese scientists report detecting all five nucleobases in the pristine asteroid samples.
Why nucleobases matter
Nucleobases are nitrogen-containing organic molecules that encode genetic information in DNA and RNA. The five major nucleobases are adenine and guanine, which are purines, and cytosine, thymine and uracil, which are pyrimidines.
Nucleobases combine with sugars and phosphate groups to form nucleotides, the building blocks of genetic material. Genetic information allows organisms to grow, reproduce and evolve.
Studying purines and pyrimidines in Ryugu samples can help scientists reconstruct the chemical history of the primordial asteroid and better understand how the building blocks of life formed and spread throughout the solar system.
Analyzing pristine asteroid material
Hayabusa2 returned a total of 5.4 grams of natural asteroid material. Because even small amounts of terrestrial contamination could affect the results, the samples were handled in ultra-clean laboratory conditions.
The researchers used water and hydrochloric acid to extract organic molecules from the material and then purified the extracts for analysis. They detected all five nucleobases in similar amounts in the two Ryugu samples they examined.
Comparisons with meteorites and asteroid Bennu
The results are consistent with earlier discoveries in space rocks, including the Murchison meteorite, which fell in Australia in 1969, and the Orgueil meteorite, which fell in France in 1864. A wide variety of organic molecules, including nucleobases, have been found in these meteorites.
Meteorites that land on Earth can potentially be contaminated during their journey through the atmosphere or after landing. By contrast, Ryugu material was collected in space and sealed before returning to Earth. Samples from the NASA mission to asteroid Bennu also yielded all five nucleobases in 2025.
Ryugu, Bennu and the parent bodies of the Orgueil meteorites are remnants of the early solar system. Their material can preserve chemical conditions from roughly 4.5 billion years ago.
These asteroids are not chemically identical. Murchison is rich in purines, while Bennu and Orgueil contain more pyrimidines. The balance may be influenced by ammonia, a key molecule that can affect which nucleobases form.
A possible cosmic source for life’s ingredients
By comparing relatively pristine Ryugu samples with meteorites such as Murchison and Orgueil, researchers are tracing the cosmic history of molecules that could support life.
The findings suggest that key components of genetic material may have formed in space and later been delivered to the early Earth. However, the precise mixture of molecules varies according to the chemical environment and history of each asteroid.
Taken together, the results indicate that carbon-rich asteroids throughout the solar system contain diverse prebiotic chemistry. The detection of all five nucleobases on Ryugu suggests that molecular components of life existed in the universe billions of years ago, making the origin of life on Earth part of a much broader cosmic chemical history.
Source: www.sciencedaily.com
