Data from the Japanese interplanetary station Hayabusa-2 indicate that fine-grained dust may exist on the asteroid Ryugu, which is part of the regolith and covers both boulders and large grains of soil. Ryugu was previously thought to be dustless. The article was published in The Planetary Science Journal.
The near-earth asteroid (162173) Ryugu was studied in detail by a spacecraft - the Japanese automatic station Hayabusa-2 not only took soil samples from the surface and from the near-surface layer of Ryugu, which it delivered to Earth at the end of last year, but also studied the asteroid from orbit around it. This body is of interest to scientists not only because of its belonging to objects of the "heap of rubble" type, which are formed as a result of the collision of two asteroids and the subsequent secondary accretion of debris, but also from the point of view of the abundance of carbon compounds in their composition, which in ancient times were asteroids could hit the early Earth.
Boulders partially covered with regolith on the surface of Ryugu. Pictures of Hayabusy-2.
A group of astronomers led by Deborah Domingue of the US Planet Institute published the results of the analysis of observations of the equatorial part of Ryugu carried out with the ONC camera and the NIRS3 near-infrared spectrometer installed on board the Hayabusa-2 in order to study the properties in more detail. regolith. At the same time, observations were carried out when the Sun was behind the station, and Ryugu was in front of the apparatus, which created good conditions for illuminating the surface of the asteroid.
Distribution map of NIRS3 observation points over the Ryugu surface.
The features of the obtained spectra indicate that one or more of the following conclusions are inadmissible for describing the Ryugu regolith: the size of the regolith particles is larger than the wavelength of the incident light, the particle sizes are the same, or the granulometric composition of the regolith is limited in size. At the same time, images of the asteroid's surface clearly show the presence of regolith grains on the Ryugu surface, which may not completely cover the entire surface of boulders, including particles several centimeters in size. The previously launched MASCOT module did not find any evidence of fine dust, but the boulders on Ryugu are very porous and can break down to form small grains that can accumulate and mix with coarser-grained regolith or even cover the grains themselves. Thus, in some areas of Ryugu, fine-grained (less than 45 micrometers) dust may exist, which is part of the granular regolith of the asteroid.
Now Hayabusa-2 is flying to the near-Earth asteroid 2001 CC21, which it will reach in July 2026. More information about the details of the mission can be found in the material "Collect the past bit by bit", and all the discoveries made by the device can be found on a separate page.