Photo/IllutrationThe light-colored part of this photo shows a section of one of the grains being studied, which measures some 50 micrometers across. (Provided by Kentaro Terada)

Scientists from Osaka University and other institutions have dated fine grains from the asteroid Itokawa, retrieved by the Hayabusa space explorer, to some 4.6 billion years ago, around the time the solar system was born.

Kentaro Terada, a professor of planetary science with Osaka University, and his colleagues analyzed fine particles, measuring about 50 micrometers across, which Hayabusa brought back to Earth in 2010. Age determination for phosphate minerals contained therein showed they had been crystallized under high temperatures some 4.6 billion years ago.

The research results were published Aug. 7 in Scientific Reports, a British science journal.

Itokawa's orbit around the sun brings it in a path between Earth and Mars. It is believed the asteroid was formed through the accumulation of broken pieces of a parent body, which had collided with another asteroid.

In addition, analysis of elements contained in the fine grains showed the parent body was hit by the other asteroid some 1.5 billion years ago.

Hayabusa 2, a successor to Hayabusa, arrived near the asteroid Ryugu in June. It is scheduled to collect sand samples from the asteroid in the months to come before returning to Earth.

“We hope our latest findings will be useful for the age determination of samples to be brought back by Hayabusa 2,” Terada said.