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Ryugu is a maniac. The surface
of the small asteroid close to the Earth is surprisingly dust-free, the observations
MASCOT Lander Show in Germany.
The asteroid, thought for
were formed from the dissolution of a larger body around 700 million years ago
there is no atmosphere to protect it from interplanetary dust passing through the solar system (SN: 27/04/19, p. 4) These miniature missiles
bombard the rocks of the exposed space 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 crossed Ryugu in October 2018 (SN online: 09/24/18), the LG took
High resolution photos showing no trace of dust-sized particles,
up to a resolution of about 100 micrometers,
on the thickness of a sheet of paper, researchers report August 23 Science.
"After a few dozen
millions of years, you should have dust on the surface, "says the planetary
The scientist Ralf Jaumann of the German Aerospace Center in Berlin. "If it's not
there you should have some kind of physical, geological processes that cleanse
up to these bodies. "
Ryugu could hide his dust in
According to Jaumann and his colleagues, porous rocks larger or deeper in its interior. tremor
because of a meteorite impact can mix the particles in larger surface rocks
or through small superficial cracks to the center of the asteroid and out of sight, the way the small nuts end up at the bottom of a cup of
mountain blend.
Or Ryugu could spray dust
in space when sunlight warms trapped ice sheets and releases volatile substances.
gases. A similar asteroid, Bennu, appears to be spreading in the space of small rock plumes, according to the NASA OSIRIS-REx spacecraft (SN:
4/13/19, p. tenBut Jaumann thinks this explanation is less likely
Ryugu. Observations of the Japanese craft Hayabusa2, which has been in orbit
Ryugu since June 2018 and which brought MASCOT, suggests that Ryugu contains less water in minerals than Bennu (SN: 1/19/19, p. 6)
There is another possible explanation
Dust Lauretta, the OSIRIS-REx chief investigator, states that Bennu dust sprays
from the University of Arizona. He thinks that Bennu's frequent temperature changes
surface when the different sides of the asteroid turn in and out of the sunlight
cause the fracture of the largest rocks of the asteroid as a cracker,
Spray crumbs in the space.
If something similar happens
on Ryugu, "Then Ryugu should also eject particles," he says. Hayabusa2
may simply not be in the right position to see the sprays. "It would be very cool
if we saw him.
But breaking stones could
create more dust, not less, he notes. A response to the mystery may not arrive before
after Hayabusa2 returned to Earth with samples of Ryugu's surface and subsoil at the end of 2020 (SN:
17/08/19, p. 14)
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