This asteroid weighs about 450 million tons and during its rotation crosses the orbit of Mars and the Earth. How its surface is cleaned is a mystery.

This near-Earth space body is the target of the Japanese probe Hayabusa-2. The mission of this probe is to take and deliver to the Earth soil samples of the asteroid. Last year, he landed several controlled robots on the surface of the Ryugu.

In the same year, Hayabusa-2 dropped a small charge on the surface of the asteroid to study the processes on its surface and in the collision of celestial bodies. A few months later, the probe itself sat on the surface of the celestial body to collect debris. It is expected that by the end of 2020 they will be on Earth.

Astronomers further study the images that come from the Hayabusa probe. The authoritative publication Science recently published the results of studies according to which the surface of the asteroid is dustless. It looks incredible because Asteroids move in the solar system for a very long time, the inevitable erosion necessarily leaves traces of dust on their surface. But even high-resolution images did not detect particles smaller than 100 microns in Ryuga.

The absence of dust on the surface of this celestial body indicates some geological process that cleans the asteroid. It is possible that there is still dust on the asteroid, but it is hidden in cracks or carried away into outer space after a collision with small meteorites.

It is possible that as the asteroid approaches the Sun, its surface begins to heat up, and the ice evaporates, taking with it small particles of dust. For example, the same phenomena were found on the surface of the asteroid Bennu. However, there is one “but”: ice reserves on the Ryuga are very far from impressive.

Presumably, the asteroid turns to the Sun in different directions and heats up unevenly. From this he is deformed. Because of this, the rocks begin to crack sharply, and some of the dust is still hidden inside the faults or spread into space.

However, today it’s just a guess. Astronomers continue to search for the answer to the question of why the surface of the asteroid is smooth. Perhaps the technology of the near future will bring us closer to the correct answers.