The space rock may hide the fine debris inside larger rocks or eject it into space
By Lisa Grossman
Ryugu is a neat freak. The surface of the small, near-Earth asteroid is surprisingly free of dust, observations from Germany’s MASCOT lander show.
The asteroid, thought to have formed from the breakup of a larger body around 700 million years ago, has no atmosphere to protect it from interplanetary dust streaming through the solar system (SN: 4/27/19, p. 4). These miniature missiles pummel exposed space rocks at high speed, breaking down their surfaces into thin layers of dust and dirt, such as those found on the moon and the asteroid Vesta.
But when MASCOT bounced across Ryugu in October 2018 (SN Online: 9/24/18), the lander took high-resolution photos that show no sign of any dust-sized particles, down to a resolution of about 100 micrometers, about the thickness of a sheet of paper, researchers report in the Aug. 23 Science.
“After a few tens of millions of years, you should have dust on the surface,” says planetary scientist Ralf Jaumann of the German Aerospace Center in Berlin. “If it’s not there, you should have some kind of physical, geological processes which clean up these bodies.”