In the process of formation, the Ryugu asteroid heated up and got wet

(ORDO NEWS) — Scientists have published the results of the first analysis of rocks and dust from the asteroid Ryugu. “We have never had such a sample. It’s incredible,” commented one of the authors of the study.

The history of these samples began eight years ago, with the takeoff of the Japanese interplanetary station Hayabusa-2. In 2019, the device landed twice on the asteroid Ryugu and collected samples of the surface and subsurface layers.

In early December 2020, the station returned to Earth with a unique cargo – several grams (5.4 grams) of clean soil. The authors of the new study were given just 125 milligrams of rocks and dust for analysis. An article with the first results was published in the journal Science .

Asteroid Ryugu belongs to the dark spectral class C (carbonaceous) – the most “popular” class, which includes 75% of known asteroids. It is believed that carbonaceous meteorites falling to Earth are fragments of such bodies, but it is difficult to identify the exact “parent” and confirm this assumption.

The main task of the Hayabusa-2 mission is precisely to learn as much as possible about the relationship between carbonaceous meteorites and asteroids and about the history of the formation of these bodies.

Analysis of the samples showed that Ryugu is similar to Iwuna-type carbonaceous chondrites (CI-chondrites). Their chemical composition coincides with the composition of the photosphere of our star.

According to scientists, they were formed at the very beginning of the formation of the solar system – even before the Sun, Earth, Moon and other bodies.

Then the system was a giant rotating cloud of gas. Most of the gas was concentrated in the center, forming the Sun, and the rest stretched into a disk, cooled and formed stones. One of them was Ryugu’s “parent”.

Judging by the composition of the fragments, at the age of one to two million years, about five million years after the formation of the entire solar system, this asteroid became saturated with water. “Imagine a cloud of ice and dust floating in space.

As it shrunk, the energy from the decay of the radioactive elements melted the ice into a giant ball of mud,” describes geochemist Nicolas Dauphas , one of three University of Chicago scientists who participated in the study led by the Japanese team.

In the process of formation the Ryugu asteroid heated up and got wet 2
The surface of the asteroid Ryugu from a height of about 6

Later, as a result of the collision, fragments broke off from that asteroid, eventually shrinking into the Ryugu asteroid. Today it looks relatively dry. According to scientists, since that moment its soil has never heated above 100 ° C. And this imposes restrictions on the likely history of the formation and “life” of bodies like it.

Geophysicist Reika Yokochi , a member of the team that examined the gases in the sample capsule, compared the whole project to trying to figure out a recipe from a soup: “We can isolate the ingredients of the soup and, from their state, determine in what order and at what temperature they warmed up.”

And analysis of the samples has already revealed differences in the composition of Ryugu and carbonaceous chondrites found on Earth.

About a dozen CI chondrites are known, all of them stayed on the planet from several decades to several centuries (the last known one fell in 1965), and then were kept in museums.

Under such conditions, it is impossible to determine how much nature has influenced their mineralogy and chemical composition. But now the experts have a “clean” sample of Ryugu.

Unlike chondrites, Ryugu has almost no sulfates, ferrihydrites, and interstratal water. Of course, this can be explained by the fact that the chondrites known to us broke off from asteroids with a higher water content. But, most likely, meteorites “infected” on Earth. This is why samples from space are so valuable.


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