Scientists to study source of high heat on asteroid

TOKYO — Japanese space experts said Thursday they will examine soil samples brought back from a distant asteroid in an attempt to find the source of heat that altered the celestial body, in their search for clues to the origin of the solar system and life on Earth.

Scientists at the Japan Aerospace Exploration Agency said they have made a preliminary examination of 5.4 grams of soil, far more than the minimum 0.1 gram sample they had hoped for, which the Hayabusa2 spacecraft brought back in December from the asteroid Ryugu, more than 300 million kilometres from Earth.

About three grams of the black granules are from Ryugu’s surface and were gathered when Hayabusa2 touched down on the asteroid in April 2019. About two grams of larger fragments, up to about one centimetre, were obtained from under the surface in a crater made by Hayabusa2 when it landed a second time three months later.

Based on near-infrared spectrophotometer analysis of data transmitted by Hayabusa2, JAXA scientists found that the asteroid was exposed to extremely high temperatures both on its surface and underground, possibly caused by an internal source of heat or planetary collisions rather than heat from the sun.

Kohei Kitazato, a University of Aizu planetary scientist working with JAXA, said his team found indications of heat exceeding 300 C both on the asteroid surface and underground.

He said the soil underground would not reach that temperature from the heat of the sun alone, suggesting that radiative internal heat or planetary collisions affected Ryugu when it was still part of a parent body billions of years ago, causing evaporation of its water.

JAXA is continuing an initial examination of the asteroid samples ahead of fuller studies next year. Scientists will also examine possible traces of organic matter in hopes they will provide insights into the origins of the solar system and life on Earth.