Five essential 'letters' of DNA and RNA found on asteroid Ryugu: A new clue to the origin of life

Samples brought from the asteroid Ryugu by Japan's Hayabusa2 mission have added new data to the debate over the origins of life. According to research published in the journal Nature Astronomy, all five nucleobases, which are among the fundamental building blocks of DNA and RNA, were detected in the samples.

The study stated that adenine, guanine, cytosine, thymine, and uracil molecules were found in the materials taken from Ryugu. These molecules are considered the "letters" of DNA and RNA, which enable the transmission of genetic information. For this reason, the finding is considered one of the significant pieces of evidence strengthening the view that the chemical building blocks necessary for life could have formed outside of Earth.

The Japan Aerospace Exploration Agency's (JAXA) Hayabusa2 spacecraft delivered a total of 5.4 grams of samples from Ryugu to Earth in 2020. The fact that the samples were taken directly from the asteroid provided the opportunity to study materials that were largely protected from the effects of Earth's atmosphere and environmental contamination.

URACIL FIRST, NOW FIVE NUCLEOBASES

Initial findings regarding organic compounds associated with life in Ryugu samples had previously come to the fore. In a study conducted in 2023, the presence of the uracil molecule had been reported. The new research, however, went beyond a single molecule and revealed that all five nucleobases, considered critical for the formation of genetic material, were present in the samples.

Researchers examined the samples in sterile laboratory conditions to identify the molecules. In the analyses performed after the organic compounds were separated using special chemical methods, it was noted that the five nucleobases were found in similar amounts in two different Ryugu samples.

These results are being evaluated alongside organic molecules previously detected in meteorites such as Murchison and Orgueil. However, while the possibility of contamination in meteorites that fall to Earth is always a subject of debate, the Ryugu samples offer a more reliable basis for comparison because they were brought back in a controlled manner.

The announcement that all five nucleobases were also found in samples collected by NASA from the asteroid Bennu suggests that similar carbon-rich asteroids may have played an important role in terms of organic chemistry in the early Solar System.

According to scientists, asteroids like Ryugu and Bennu are "time capsules" remaining from the formation period of the Solar System. The chemical traces preserved in these objects could help us understand which molecules formed in space before life emerged and how these building blocks might have been transported to the early Earth.