The nitrogenous bases that make up ribonucleic acid (RNA) are adenine, guanine, cytosine and uracil. The latter has already been detected in small samples from the Ryugu asteroid. They were picked up in 2019 by the Japan Aerospace Exploration Agency (JAXA) Hayabusa2 probe at two different landing sites and brought to Earth in a capsule, which crashed over a desert area in Australia in December 2020.
The study suggests that nucleobases, such as the uracil found in Ryagu, have an extraterrestrial origin and reached Earth through carbon-rich meteorites.
The Japanese researchers who analyzed them report Tuesday in the journal Nature Communications the discovery of uracil and another important component of the metabolism of terrestrial life: vitamin B3 or niacin, in addition to some organic molecules considered relevant for synthesizing more complex ones.
The authors point out that these substances could have led to the appearance of the first life on Earth. The same team had already found them in meteorites falling on our planet, but their detection in virgin material coming directly from Ryugu points to an extraterrestrial origin, which could then arrive through carbon-rich meteorites.
“The present study strongly indicates that this type of prebiotic interest molecules commonly formed in carbonaceous asteroids, including Ryugu, and that reached the early Earth”, explain the scientists in their research, led by Professor Yasuhiro Oba, from the University of Hokkaido.
From interstellar ice to asteroid
The researchers point out that these types of compounds may have been generated by photochemical reactions in interstellar ice, which would later be incorporated into asteroids as the solar system formed.
Ultraviolet rays and cosmic radiation may have further altered them over millions of years. The arrival of these compounds to Earth by meteorite impacts may have played an important role in the emergence of the genetic functions of early life, the authors conclude.
After collecting the samples from the asteroid Ryagu, the Hayabusa2 spacecraft placed them in a capsule in Astralia. Below, two of which have already been used in the detection of uracil and other biomolecules. / JAXA/Yasuhiro Oba et al./Nature Communications
Reference:
Yasuhiro Oba et al. “Uracil on carbonaceous asteroid (162173) Ryugu”. Nature Communications, 2023.