Asteroid Ryugu has all the major ingredients for life

All five major components of DNA and RNA were found in samples from the asteroid Ryugu. This reinforces the idea that asteroids may have brought ingredients for the first living organisms on Earth long ago.

Japan’s Hayabusa 2 spacecraft visited Ryuga in 2018, firing two projectiles—one small and one large—at the asteroid’s surface and collecting the resulting debris. It arrived back on Earth with the samples in 2020, and researchers have been analyzing them in detail ever since.

Yasuhiro Oba at Hokkaido University in Japan and his colleagues examined two samples, one from the surface of the asteroid and one composed of subsurface materials excavated by 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 sugars and phosphoric acid.

This is not the first time that nucleobases have been found in asteroid samples: they have also been observed in meteorites and in samples from the asteroid Bennu. However, the researchers found different amounts of different nucleobases among the different samples, suggesting that these compounds could be useful for tracing asteroids and meteorites back to the parent bodies from which they separated in the distant past, as well as understanding the evolution of those parent bodies over time.

The fact that nucleobases have been found in samples from asteroids like Bennu and now Ryugu speaks to the potential importance of asteroids in the history of life on Earth. “Their detection in Ryugu strongly supports their ubiquity in the solar system,” says Oba. If asteroids throughout the solar system are full of DNA building blocks, they could have brought them to Earth billions of years ago and helped jump-start 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 to the origins of life on Earth.

topics:

• asteroids/
• extraterrestrial life