Parent body of asteroid Ryugu formed early in solar system history, study finds

A research team from Hokkaido University and other institutions said Friday that the parent celestial body of the asteroid Ryugu formed within 2 million years of the birth of the solar system about 4.6 billion years ago.

The findings were published in the U.S. scientific journal Science.

The team analyzed minerals in sand samples collected from Ryugu, which were brought back by Japan’s Hayabusa2 asteroid probe in 2020.

The sand samples contain minerals and organic substances that formed through reactions between rock and water produced by the melting of ice as temperatures inside its parent body gradually increased due to heat generated by radioactive materials.

Until now, the timing of the formation of these materials, as well as the parent body, itself, had remained uncertain.

Hokkaido University Associate Professor Noriyuki Kawasaki and other researchers analyzed the age of dolomite, a carbonate mineral found in the Ryugu samples, by using radioisotopes. They improved accuracy by adopting a new error-correction method and reproduced the temperature changes inside the parent body through computer simulation.

The analysis revealed that dolomite formed about 4.56 billion years ago in an environment of around 90 degrees Celsius.

Considering the time required to reach this temperature, the team concluded that Ryugu’s parent body formed within 2 million years of the start of the solar system’s formation.