Scientists analyzing newly allocated material from asteroid Ryugu have identified all five canonical nucleobases, the fundamental molecular components of DNA and RNA.
Ryugu is an ancient, carbonaceous body rich in organic compounds. The Hayabusa2 mission, operated by the Japan Aerospace Exploration Agency, retrieved Ryugu material in 2020. The spacecraft touched down twice on the asteroid’s surface and collected subsurface grains.
The asteroid is considered a relatively unaltered remnant from the solar system’s earliest period. The identification of the complete set of standard nucleobases in these samples extends previous evidence that such biologically relevant molecules are not unique to Earth and can form and persist in the cold, chemically diverse environments of small bodies.
“This result supports the idea that important components of life exist everywhere in the universe,” biogeochemist Toshiki Koga said, according to Mainichi Shimbun.
Most comprehensive finding to date
The current findings are the most comprehensive detection of the compounds in extraterrestrial samples from a primitive asteroid to date. Earlier work had confirmed only uracil because initial material was too scarce. The latest studies, using 20.2 milligrams of returned grains, revealed adenine, guanine, cytosine, thymine, and uracil together in the same sample, according to Science Alert.
The five building blocks—adenine, cytosine, guanine, thymine, and uracil—are essential components of the genetic polymers DNA and RNA. These polymers encode and transmit biological information. Scientists are increasingly comparing organic inventories across different small bodies to trace how their chemistry diverged over time.
In addition to Ryugu, asteroid Bennu—sampled by NASA’s OSIRIS-REx mission—has also yielded all five canonical nucleobases. This indicates their presence on two carbonaceous asteroids. Researchers have contrasted the nucleobase content from these asteroids with that of well-studied meteorites such as Murchison and Orgueil. They observed differences in the ratios of purines to pyrimidines and in overall composition. The variations point to distinct chemical histories for each object, with factors such as ammonia availability, the presence and longevity of liquid water, temperature regimes, and the duration of synthesis influencing which compounds formed and how they were preserved.
A chemical inventory from space
Taken together, the detections suggest a solar system in which organic chemistry was both widespread and locally shaped by environmental conditions. The presence of the nucleobases in the samples reinforces the hypothesis that carbonaceous asteroids contributed to the prebiotic chemical inventory of the early Earth.
By delivering organics during impacts, such bodies could have enriched the young planet’s surface with molecular precursors relevant to the emergence of life. This possibility aligns with a broader hypothesis that amino acids and sugars—the sources of energy and components of the human body—were brought to Earth from space. Meteorites and related debris acted as carriers.
This article was produced with the assistance of a news discovery technology.