5 ‘Letters’ of DNA Found on Ryugu

Scientists have found all five “letters” of DNA in a “potentially hazardous” asteroid, suggesting the key ingredients for life may be common in the solar system.

Researchers analyzing samples from the Ryugu space rock, a 3,000-foot-wide asteroid shaped like a spinning top, made this discovery.

Research Findings

Scientists found the building blocks for DNA, a complete set of canonical nucleobases, the genetic foundation for all life on Earth, as well as RNA, according to a study published on March 16, 2026, in the journal Nature Astronomy.

The study’s lead author, and biochemist at the Japan Agency for Marine-Earth Science and Technology, Toshiki Koga, told AFP, this “does not mean that life existed on Ryugu. Instead, their presence indicates that primitive asteroids could produce and preserve molecules that are important for the chemistry related to the origin of life.”

In 2023, NASA discovered the same nucleobases on asteroid Bennu via the OSIRIS-REx spacecraft. Together, the findings suggest the nucleobases could be throughout the solar system.

Origins of Life?

Scientists do not know how life on Earth began. There are some researchers who believe life began on Earth. Others posit that life, or at least the building blocks of life, originated elsewhere and were carried to Earth via asteroids or comets.

Astrobiologist at the University of Alcalá in Spain César Menor Salván stated in an interview that the new results “do not suggest that the origin of life took place in space.” However, “with this and the results from Bennu, we have a very clear idea of which organic materials can form under prebiotic conditions anywhere in the universe.”

The Ryugu samples were collected as part of the Hayabusa2 mission by the Japan Aerospace Agency (JAXA), launched in 2014. The unmanned spacecraft landed on the asteroid in 2019 and collected dust samples from the surface before returning to Earth in 2020.

The samples weighed 5.4 grams each, less than the weight of a quarter. Preliminary analysis in 2023 discovered that the asteroid contained many of the building blocks for life, including one nucleobase and several other organic materials, such as 15 amino acids, which are the foundation of proteins. They are prebiotic molecules found in all life.

5 ‘Letters’ of Life

All of the nucleobases were discovered: adenine, guanine, cytosine, thymine, and uracil. The natural compounds that mix with ribose and phosphate to form DNA and RNA, and compared them to the ratio of nucleobases from Bennu, and two other meteorites: Murchison and Orgueil.

Adenine and guanine are purines known for a double-ring structure. Cystosine, thymine, and uracil are single-ring-structured pyrimidines.

Researchers learned Ryugu contained equal amounts of purines and pyrimidines. Bennu and Orgueil contained more enriched pyrimidines, and Murchison was more enriched with purines. Additionally, scientists identified a significant correlation between the purine-pyrimidine ratio and ammonia in Ryugu, Bennu, and Orgueil. This indicates ammonia may have been a key factor in the nucleobase formation pathways in asteroid environments, according to the study.

Koga says, “Because no known formation mechanism predicts such a relationship, this finding may point to a previously unrecognized pathway for nucleobase formation in early solar system materials.”

Ryugu and Bennu are carbonaceous asteroids, which make up 75 percent of all the asteroids in the solar system. Observations from the James Webb Space Telescope (JWST) indicate that both asteroids originated from the same parent space rock. The Orgueil also originated from a carbonaceous asteroid. This discovery suggests to scientists that carbonaceous asteroids helped Earth gain life-forming chemicals.

“The detection of diverse nucleobases in asteroid and meteorite materials demonstrates their widespread presence throughout the Solar System and reinforces the hypothesis that carbonaceous asteroids contributed to the prebiotic chemical inventory of early Earth,” according to the research study.

Sources:

LiveScience: All 5 ‘letters’ of DNA found on an asteroid speeding through our solar system. What do they tell us about the origin of life?
Phys.org: Ryugu asteroid samples contain all DNA and RNA building blocks
Space.com: Ryugu asteroid sample contains all five key components of DNA

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