Ryugu is an asteroid that sometimes passes close to Earth
JAXA
All five main ingredients for DNA and RNA have been found in samples from the asteroid Ryugu. This strengthens the idea that asteroids may have brought the ingredients of the first living organisms to Earth long ago.
Japan’s Hayabusa 2 spacecraft visited Ryugu in 2018, where it fired two projectiles – one small and one large – into the surface of the asteroid and collected the resulting debris. It returned to Earth with the samples in 2020, and scientists have been analyzing these in detail ever since.
Yasuhiro Oba of Hokkaido University in Japan and his colleagues examined two samples, one from the asteroid’s surface and one consisting of subsurface materials excavated by the projectiles. In both, the team found all five primary nucleobases, which are the compounds that make up the nucleic acids DNA and RNA when combined with sugar and phosphoric acid.
This is not the first time that nucleobases have been found in asteroid samples: they have also been seen in meteorites, and in samples from the asteroid Bennu. However, the researchers found different amounts of the different nucleobases among the different samples, suggesting that these compounds may be useful for tracing asteroids and meteorites back to the parent bodies from which they broke in the distant past, as well as understanding the evolution of these parent bodies over time.
The fact that nucleobases have been found in samples of asteroids such as Bennu and now Ryugu speaks to the potential importance of asteroids in the history of life on Earth. “Their discovery in Ryugu strongly supports their ubiquity in the solar system,” says Oba. If asteroids across the solar system are full of the building blocks of DNA, they could have brought them to Earth billions of years ago and helped initiate the evolution of life.
It is even possible that Ryugu and other asteroids have DNA and RNA on them, not just their components. “It is very likely that more complex organic molecules such as nucleic acids form on asteroids,” says Oba. This could make asteroids even more important for the origin of life on Earth.
Topics:
- asteroids/
- extraterrestrial life
