A new study has detected all five major nucleobases—the molecular “letters” of genetic information—in pristine samples collected from the asteroid Ryugu. The findings, based on material returned to Earth by the Japan Aerospace Exploration Agency’s (JAXA) Hayabusa2 mission, suggest that important components of DNA and RNA may have formed in space and been available to the early Earth.
Asteroid particles provide a rare view of the chemistry that may have contributed to the origin of life. The Ryugu samples were returned from space in 2020 by Hayabusa2.
In 2023, an international team reported finding uracil, one of the five nucleobases, in the samples. Now, a team of Japanese scientists has confirmed the presence of all five in the pristine asteroid material, according to a study published in Nature Astronomy.
The result indicates that these fundamental components of life may have been distributed throughout the solar system during its early history.
Why scientists look for nucleobases
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 phosphates to form nucleotides, the building blocks of genetic material. Without them, there would be no genetic code to enable organisms to grow, reproduce and evolve.
By examining the purines and pyrimidines in Ryugu samples, scientists can investigate the chemical history of this primordial asteroid and improve their understanding of how the building blocks of life formed and spread through the solar system.
Analyzing pristine asteroid material
Hayabusa2 returned a total of 5.4 grams of natural asteroid material. Because contamination from Earth could affect the results, the samples were handled under ultra-clean laboratory conditions.
The researchers used water and hydrochloric acid to extract organic molecules from the material, then purified the extracts for further analysis. They detected all five nucleobases in similar amounts in the two Ryugu samples they examined.
The building blocks of genetic material in space
The findings are consistent with earlier discoveries in space rocks. A wide variety of organic molecules, including nucleobases, has been found in the Murchison meteorite, which fell in Australia in 1969, and the Orgueil meteorite, which fell in France in 1864.
Meteorites that land on Earth can be altered or contaminated during their journey and after impact. However, samples collected directly from asteroids provide a less disturbed record. In 2025, all five nucleobases were also detected in pristine samples from NASA’s asteroid Bennu mission.
Ryugu, Bennu and the parent bodies of the Orgueil meteorites are remnants of the early solar system. Their materials may have remained almost unchanged for about 4.5 billion years.
These asteroids nevertheless show chemical differences. Murchison is rich in purines, while Bennu and Orgueil contain more pyrimidines. Researchers think this balance may be influenced by ammonia, a key molecule that can affect which nucleobases form.
By comparing relatively pristine Ryugu samples with meteorites such as Murchison and Orgueil, scientists are tracing the cosmic history of molecular components that could support life.
A possible route for life’s ingredients to reach Earth
Taken together, the findings suggest that carbon-rich asteroids throughout the solar system contain diverse prebiotic chemistry. The exact mixture of molecules—including the balance between purines and pyrimidines—varies according to each asteroid’s chemical environment and history.
Because the Ryugu samples were collected in space and protected from terrestrial contamination, they offer one of the clearest views yet of the ancient solar system’s chemistry.
The detection of all five nucleobases on Ryugu suggests that the molecular components of life may have formed in the universe billions of years ago. Asteroids may then have helped deliver these ingredients to the early Earth, linking the origin of life on our planet to the chemistry of ancient bodies across the solar system.
Source: www.sciencedaily.com