Japan’s Asteroid Sample Contains All Five Genetic “Letters” Of DNA And RNA, Supporting Idea That Life’s Ingredients Came From Space

Scientists have confirmed the presence of all five chemical building blocks of DNA and RNA in pristine samples from asteroid Ryugu, strengthening the hypothesis that the key ingredients for life on Earth may have arrived from space.

The discovery was published on Mar. 16, 2026, in the journal Nature Astronomy by a team of Japanese scientists led by JAXA biogeochemist Toshiki Koga from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).

The five nucleobases, adenine, guanine, cytosine, thymine, and uracil, are often called the genetic "letters" of life because they encode and transmit genetic information in DNA and RNA, according to Daily Galaxy.

The Ryugu samples were returned to Earth in December 2020 by JAXA's Hayabusa2 spacecraft, which launched in 2014 and landed on the 900-meter-wide, spinning-top-shaped asteroid in 2019.

The mission returned approximately 5.4 grams of material, far exceeding the mission's minimum requirement of 0.1 grams, collected from two different sites on the asteroid's surface and subsurface.

Earlier research in 2023 had detected only uracil in the Ryugu samples. For the new study, Koga's team was granted access to two additional aggregate samples and used more advanced analytical techniques to conduct a comprehensive nucleobase analysis previously impossible due to limited sample volume.

Crucially, the researchers also found structural isomers, related molecules with the same chemical formula but different arrangements, including 6-methyluracil, a compound that does not naturally occur on Earth.

This finding is considered strong evidence that the nucleobases are not contamination from Earth but were genuinely formed through non-biological processes in space, C&EN reported.

Koga told AFP that the results "does not mean that life existed on Ryugu," but rather that "primitive asteroids could produce and preserve molecules that are important for the chemistry related to the origin of life."

These findings align with a separate discovery from NASA's OSIRIS-REx mission, which found all five nucleobases in samples from asteroid Bennu in 2023. The detection of the same genetic building blocks on two separate asteroids suggests these molecules were "universally generated during the formation of the solar system."

The findings support what scientists call pseudo-panspermia, the idea that key organic molecules used by life originated in space and were later delivered to early Earth by asteroids or meteorites.

Astrobiologist César Menor Salván of the University of Alcalá in Spain noted that "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 researchers plan to expand their analysis to other solar system materials to better understand the relationship between nucleobase composition and ammonia concentration, which appears to play a key role in how these molecules form in space, as per Gigazine.