(ORDO NEWS) — Planetary scientists working with samples of the substance of the asteroid Ryugu, obtained by the Hayabusa-2 station, presented the first results of the analysis of soil particles in laboratory conditions. It turned out that Ryugu’s substance is very porous and contains many hydrated compounds and organic substances, but is poor in chondrules. Articles (1, 2) were published in the journal Nature Astronomy.
On December 6, 2020, the Hayabusa-2 interplanetary station successfully delivered to Earth a return capsule with several grams of soil collected from the near-Earth asteroid Ryugu, which belongs to the C-class. In total, two attempts were made to take soil – in February and July 2019.
The first sample (compartment “A”, 3.23 grams of soil) contains material from the surface of the asteroid, and the second (compartment “C”, 2.025 grams of soil) – from the near-surface layer ejected during the creation of a 15-meter man-made crater. At the end of December last year, Ryugu’s soil was completely removed from the container and sent for storage and research.
Two groups of planetary scientists presented the first results of the analysis of soil particles to Ryugu. A group led by Toru Yada from the Institute of Space and Astronautics in Sagamihara was researching the physical properties of the soil and its approximate mineralogical composition.
Soil particle sizes ranged from 8 millimeters to submillimeter sizes, with most of the millimeter particles being. At the same time, there were more particles with a size of more than three millimeters in compartment “C” than in compartment “A”. The surfaces of the soil grains were either uneven or smooth.
The average calculated bulk density of Ryugu particles was 1,282 kilograms per cubic meter, which is less than that of meteorites such as CI chondrites and meteorite from Lake Tagish (the most porous meteorite ever found on Earth) and slightly higher than the bulk density of Ryugu itself, determined based on observations of the station and amounted to 1190 kilograms per cubic meter. This indicates a high (about 46 percent) micro porosity of the soil, which was not previously observed for the material of meteorites.
The low albedo of the soil in the optical and near infrared ranges and the features of the reflection spectra indicate an abundance of carbon in the Ryugu matter and the presence of a hydroxyl group OH, which indicates that the parent body of the asteroid was exposed to water.
At the same time, almost no submillimeter inclusions rich in calcium and aluminum (calcium-aluminum-rich inclusion, CAI) and chondrules were found, however, there are many bright, spotty, small inclusions. In general, Ryugu looks more like CI chondrites than any other type of meteorite, but has a lower albedo, high porosity and fragility.
A group of researchers led by Cédric Pilorget from the Institute for Space Astrophysics at the University of Paris-Saclay presented the results of studies of the mineralogical composition of Ryugu soil using a MicrOmega hyperspectral microscope operating in the near infrared range.
The data collected indicate compounds rich in OH, CH and NH, such as carbonates (some of which are enriched in iron), aluminum hydroxide, phyllosilicates, hydrated salts, and nitrogen-rich organics.
Thus, the samples collected by “Hayabusa-2” turned out to be one of the most primitive substances that were investigated in terrestrial laboratories. Perhaps they will contribute to the revision of theories of the origin and evolution of the solar system.
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