The first X-rays of asteroid Ryugu: dark and highly porous – science – life

Dark, with high porosity and a heterogeneous composition at the microscopic level. This is how Ryugu appears, a diamond-shaped asteroid with a diameter of about one kilometer, and in December 2020, the Japanese spacecraft Hayabusa2 returned samples from its surface, about 5.4 grams.

Now the magazine natural astronomy He publishes in two articles a preliminary examination of this first material transported to Earth from an asteroid rich in carbon, which may give clues about the early history of the solar system and about the formation of organic and hydrated minerals, the building blocks of life.

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The Japanese probe Hayabusa 2, after a journey of six years and 5.2 billion kilometers, dropped a container with a small amount of dust and gas from the asteroid Ryugu on December 6, 2020 in Australia.

Hayabusa2 landed twice on the asteroid’s surface in 2019 to collect samples and the first analyzes were carried out on Earth on December 10 and 11 last year, in a laboratory of the Japan Aerospace Exploration Agency (JAXA), located in the town of Sagamihara, southwest of Tokyo.

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From this first examination it was concluded that the gas in the container was derived from Ryugu. The capsule also carried small stones several millimeters in size. All of this material, as JAXA said in its day, is interesting for advancing the knowledge of the origin of our solar system, finding key details about the formation of the asteroid Ryugu, 4.6 billion years ago, and better understanding its affinity with a class of meteorites called carbonaceous chondrites.

In the first two papers now published, Toru Yada and colleagues from JAXA found that the sample is very dark — it reflects only 2 percent of the light that strikes it — with a high porosity of 46 percent. hundred, larger than that of any meteorite studied thus far.

In the second article, Cedric Bellorget and his team, from the University of Paris-Saclay, determined the composition of the samples using a microscope capable of acquiring images at different wavelengths of light in the visible and infrared spectra.

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According to the analysis, it consists of a moist, clay-like matrix, with a variety of organic elements embedded. However, some of the individual parts are made up of different substances, such as carbonates or volatile compounds.

The presence of volatiles rich species, possibly from the outer solar system, would support the fact that Ryugu has preserved both the original material and the altered phases, which are now available for careful analysis in the laboratory, with the potential to glean new insights into the paths of formation and evolution of objects. Planetary in our solar system.

These results reveal the heterogeneous microscopic composition of the Ryugu samples, confirming the ‘in situ’ observations made by Hayabusa2, which indicate that this asteroid is microscopically uniform in structure and composition—similar to carbon-rich chondrite meteorites—, but that it is darker, more porous and brittle.

Thus, with these data, the researchers conclude that Ryugu is more similar to these chondrites but has lower albedo (the ratio between light energy hitting the surface and that being reflected), higher porosity and more brittle properties.

The authors, noting that the physical and chemical properties did not change during the asteroid’s return, concluded that the content of these samples appears to be among the most abundant raw materials available in laboratories to date.

This constitutes a “unique group” for studying the origin and evolution of our solar system, while serving as a model for the return of planetary samples in the future.