New study of Ryugu samples, along with findings from asteroid Bennu, strengthens hypothesis that carbonaceous asteroids provided early Earth with important starting materials for the chemistry of life
A new study in Nature Astronomy has identified adenine, guanine, cytosine, thymine, and uracil in samples from the asteroid Ryugu. Together with the findings from the asteroid Bennu, a consistent picture emerges: carbonaceous asteroids in the early solar system carried important starting materials for prebiotic chemistry. However, the researchers emphasize that this is not evidence of life in space, but of a list of ingredients that was available before life appeared on Earth. (Nature)
The new study, led by Toshiki Koga and his colleagues, was based on samples brought back to Earth by the Japanese Hayabusa2 spacecraft from the asteroid Ryugu. As early as 2023, uracil, one of the bases of RNA, was reported to have been found on Ryugu; now, with more material and improved analytical methods, the other four bases—adenine, guanine, cytosine, and thymine—have also been identified in two samples, making Ryugu the first to have a complete set of the five canonical bases of DNA and RNA. The samples themselves are considered particularly valuable because they were collected directly from a carbonaceous asteroid and returned to Earth in 2020 with almost no exposure to the terrestrial environment, and therefore provide a relatively clean window into the chemistry of the early solar system.
The finding does not mean that complete DNA or RNA existed on Ryugu, and certainly not that life itself originated there. The nitrogenous bases are only part of the hereditary molecules. Still, it is a very important part: these are the “letters” of the genetic code. The researchers write that the presence of all five bases in carbonaceous asteroids strengthens the hypothesis that such bodies contributed to the prebiotic chemical inventory of the ancient Earth. Outside experts also emphasize the distinction: the finding does not prove that life originated in space, but rather helps to understand which organic molecules could have formed under prebiotic conditions and been preserved in ancient bodies.
The finding does not prove that life originated in space.
This is where Bennu, the asteroid from which NASA returned samples on the OSIRIS-REx mission, comes into play. In 2025, NASA reported that Bennu samples contained all five nitrogenous bases and 14 of the 20 amino acids used to build proteins on Earth. Later, in December 2025, the discovery of ribose — the sugar of RNA — and glucose was also reported. An article in Nature Geoscience emphasized that Bennu had already contained all five bases, phosphates, and ribose, i.e., all the ingredients needed for RNA. Therefore, when you combine Bennu with Ryugu, you get a broader picture: important starting materials for biochemistry are not unusual for a single celestial body, but were probably quite common in the young solar system.
One of the most interesting aspects of the study is not the discovery of the bases themselves, but the differences in their composition from other samples. Almost equal amounts of purines and pyrimidines were found in Ryugu. In contrast, in the Murchison meteorite there is a clear preference for purines, while in the Bennu samples and the Orgei meteorite there is a preference for pyrimidines. The researchers also found a strong negative correlation between the ratio of purines to pyrimidines and the concentration of ammonia. According to them, this may indicate different chemical formation pathways in different ancient bodies, and may in the future serve as a molecular marker that will help reconstruct the conditions of the formation and evolution of carbonaceous asteroids. External experts also marked the connection to ammonia as the most innovative point in the work.
The chemicals needed for life are common in space
Why is this important to the origin of life question? Because the debate is not just about whether “life came from space,” but what ingredients arrived on Earth before life, and what kind of chemistry was already available here when conditions became right. If carbonaceous asteroids carried nitrogenous bases, amino acids, sugars, phosphates, and ammonia, then they could have served as a natural delivery system that enriched the early Earth with a variety of raw materials. This still doesn’t solve the question of exactly how the first replicating molecules formed or how a living system actually emerged, but it greatly reduces the uncertainty about the “grocery list” that was available at the beginning.
Another reason for caution is that even the most impressive findings depend heavily on the quality of the sample. One of the great contributions of sample-return missions like Hayabusa2 and OSIRIS-REx is that they allow us to work with almost pristine material, without the contamination and weathering that meteorites undergo after they fall to Earth. So the comparison between Ryugu, Bennu, Orgei, and Murchison is not just a collection of chemical anecdotes, but a better basis for mapping the organic chemistry of ancient bodies. In this sense, Ryugu is not “proof of life,” but more strong evidence that the young universe produced and preserved important ingredients for life long before Earth became a habitable world.
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One response
Any organic material that would have crashed on Earth would have burned in the heat of entry or the heat of the explosion on contact with the ground. This is certainly not the origin of life. PS - It is absolutely true that there has not yet been a real, proven scientific explanation for the way life arose. Honestly, from all the knowledge I have accumulated over the years of my life, I only understood that the world is too complex to have been created through trial and error.