After analyzing the footage produced by the German satellite MASCOT lander, scientists noticed that the surface of the asteroid Ryugu is dust-free.
It is believed that the asteroid Ryugu was formed by the collapse of a larger body approximately 700 million years ago. It has no atmosphere to keep dust from passing through the solar system. In fact, these are microscopic "rockets" that bombard the surface of the asteroid and break it into dust fragments. Exactly the same dust is found on the Moon and the asteroid Vesta.
In the fall of 2018, a German probe took high-resolution photographs of Ryugu's surface, which showed no small particles. The photographing resolution was set to 100 micrometers, which is close in thickness to a sheet of paper.
Planetologist Ralph Jaumann says that after several tens of millions of years, dust must appear on the surface, but if it is not there, then some physical or geological processes take place on the asteroid that rid the space body of dust.
According to Yaumann, the asteroid Ryugu can hide dust in porous rocks or deep inside a space body. When the asteroid is shaken by a meteorite impact, the particles fall through small cracks towards the center of the asteroid.
There is another version of events: dust is sprayed into space along with volatile gases that arise when pieces of ice are heated by sunlight.
According to NASA's OSIRIS-REx probe, the asteroid Bennu is spewing out streams of small rocks into space. However, Jaumann believes that this option is not suitable for Ryugu. Recent studies of the asteroid have shown that it has fewer minerals than Bennu.
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Researchers at the University of Arizona have another explanation for Bennu's dust streams. Perhaps the very frequent temperature changes on the asteroid's surface cause large rocks to break, releasing dust particles into space like a broken cracker.
Researchers believe that something similar is happening on Ryugu, just the Hayabusa2 probe is not in the right position to see this phenomenon. However, rock fragments can generate significantly more dust. Perhaps we will be able to find out the answer to this riddle as soon as Hayabusa2 sends soil samples taken from the bowels of Ryugu to Earth in 2020.
Andrey Vetrov