(JAXA)
Data from the Japanese interplanetary station Hayabusa-2 indicate that fine-grained dust may exist on the asteroid Ryugu.
The dust is part of the regolith and covers both boulders and large grains of soil. Ryugu was previously thought to be dustless.
The near-earth asteroid (162173) Ryugu was studied in detail by the Japanese spacecraft Hayabusa-2.
The mission not only took soil samples from the surface and from the near-surface layer of Ryugu, but also studied the asteroid from orbit around it.
This body is of interest to scientists because it belongs 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.
Ryugu is important 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.
A group of astronomers led by Deborah Domingue from the US Planet Institute published the results of the analysis of observations of the equatorial part of Ryugu.
The team used the ONC camera and the NIRS3 near-infrared spectrometer, installed on board Hayabusa-2, in order to study the properties in more detail regolith.
At the same time, the observations were carried out when the Sun was behind the station, and Ryugu was in front of the spacecraft. This created good conditions for illuminating the surface of the asteroid.
The features of the obtained spectra indicate that one or several of the following conclusions are inadmissible for describing the Ryugu regolith.
For example, the size of the particles of the regolith is larger than the wavelength of the incident light, the sizes of the particles 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, 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.
However, 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.
Source:
- The Planetary Science Journal: https://iopscience.iop.org/article/10.3847/PSJ/ac14bb