Left: Photograph of rocks recovered by Hayabusa2 from the asteroid Ryugu. Right: enlarged image of the structure of one of the pieces, taken with an electron microscope. Credit: JAXA / Yokoyama et al.
After a six-year journey, a spacecraft called Hayabusa2 returned to Earth’s atmosphere in late 2020 and landed in the depths of Australia’s interior. When investigators from the Japanese space agency JAXA opened it, they found its precious payload sealed and intact: a handful of dirt that Hayabusa2 managed to remove from the surface of an asteroid at high speed.
Scientists have now begun to announce the first results of the analysis of this extraordinary sample. What they found suggests that this asteroid is a piece of the same matter that joined our sun four and a half billion years ago.
“Previously we only had a handful of these rocks to study, and they were all meteorites that fell to Earth and were stored in museums for decades or centuries, which changed their composition,” said geochemist Nicolas Dauphas. one of three from the University of Chicago Researchers who worked with an international team of scientists led by Japan to analyze the fragments. “Having pristine samples of outer space is just amazing. They are witnesses to parts of the solar system that we would not otherwise have explored.”
‘It’s spectacular’
In 2018, Hayabusa2 landed on a moving asteroid called Ryugu and collected particles from above and below its surface. After spending a year and a half orbiting the asteroid, it returned to Earth with a sealed capsule containing about five grams of dust and rock. Scientists around the world have been eagerly awaiting the unique sample, one that could help redefine our understanding of how the planets evolve and how our solar system was formed.
Scientists are especially excited that these particles would never have reached Earth without the protective barrier of a spaceship.
“In general, all we get to study asteroids are pieces that are large enough to reach the ground like meteorites,” said UChicago geochemist Andrew M. Davis, another member of the analysis team. . “If you took this handful and dropped it into the atmosphere, it would burn. You would lose it and there would be a lot of evidence about the history of this asteroid.
“We haven’t really had a show like this before. It’s spectacular.”
Petrography of the Ryugu sample. (A) Image of backscattered electrons (BSE) from the Ryugu A0058-C1001 sample. The black space in the figure is a pore. (B) Combined elementary map of the same sample, with X-rays characteristic of Ca Kα, Fe Kα and S Kα lines assigned to the RGB color channels as indicated in the legend. The minerals carbonate (dolomite), sulfur (pyrrhotite) and iron oxide (magnetite) are embedded in a matrix of phyllosilicates and, in some cases, precipitate into small veins. The texture of the sulfur is similar to that of the ungrouped chondrite of Flensburg. (C) Ternary diagram between Fe, Mg and Si + Al showing the bulk chemical compositions of the phyllosilicates in A0058-C1001. Black lines are solid solution compositions for serpentine and saponite. Each open red circle shows the bulk chemical composition of the phyllosilicates measured at various locations in panels A and B, each location being 5-10 μm square. We have chosen each size to exclude minerals other than the phyllosilicates in the area. Bulk compositions differ from place to place, with a distribution indicating that the phyllosilicates consist of serpentine and saponite with varying Fe / Mg ratios. The uncertainties of each measurement are smaller than the size of the symbol. (D) BSE image of the Ryugu C0002-C1001 sample, showing the broken matrix. The texture is similar to CI chondrites. Credit: Science (2022). DOI: 10.1126 / science.abn7850
Davis, Dauphas, and Uchicago colleague Reika Yokochi are part of a team that came together to help Japanese researchers analyze the samples. Every part of the contents of the capsule is being studied rigorously. Yokochi is part of a team that is analyzing gases that were trapped in the capsule or dirt. Dauphas and Davis are part of a team that is studying the chemical and isotopic compositions of grains to reveal their history.
The first compilation of these results, reported in Science on June 9, she reveals Ryugu’s makeup.
The rock is similar to a class of meteorites known as “Ivuna-type carbonaceous chondrites”. These rocks have a chemical composition similar to that we measure from the sun and are believed to date back to the beginnings of the solar system about four and a half billion years ago, before the formation of the sun, moon and earth. [should Moon be capitalized to distinguish it from other moons?]
At that time, all that existed was a giant, revolving cloud of gas. Scientists think most of this gas crawled toward the center and formed the star we know as the sun. As the remnants of this gas expanded into a disk and cooled, it was transformed into rocks, which today still float around the solar system; it looks like Ryugu may be one of them.
Scientists said the fragments show signs of being soaked in water at some point. “One has to imagine an aggregate of ice and dust floating in space, which became a giant ball of mud when the ice melted by nuclear power due to the disintegration of the radioactive elements that were present in the asteroid when it formed, “Dauphas said. But surprisingly, today the rock looks relatively dry.
The surface of the asteroid Ryugu from an altitude of 6 km. Credits: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University, AIST
Using radioisotope dating, they estimated that Ryugu was altered by water circulation only about five million years after the formation of the solar system.
These findings are especially interesting to researchers because they hint at similar formation conditions between comets and some asteroids like Ryugu.
“By examining these samples, we can restrict the temperatures and conditions that must have occurred throughout his life and try to understand what happened,” Yokochi explained.
He compared the process to trying to figure out how to make a soup, but only with the end result and not the recipe: “We can take the soup and separate the ingredients, and try to know from its conditions how much it has been heated and in what order “.
The scientists noted that a percentage of the finding will be set aside so that we can analyze them in the future with more advanced technology, as we did with lunar samples from Apollo.
“After having Apollo moon samples 50 years ago, our ideas about how the moon formed completely changed,” Davis said. “We are still learning new things from them, because our instruments and technology have advanced.
Scientists from the Japanese Space Agency traveled to the interior of Australia to retrieve the capsule containing pieces extracted from the surface of an asteroid in speed by the Hayabusa2 spacecraft in December 2020. Credit: JAXA
“The same thing will happen with these samples. This is a gift he continues to give.”
This mission is the first of several international missions that will carry samples of another asteroid called Bennu, as well as unexplored areas of our moon, Mars and the moon of Mars Phobos. All this should happen in the next 10 or 20 years.
“It has been far under the radar of the public and some decision makers, but we are entering a new era of planetary exploration that is unprecedented in history,” Dauphas said. “Our children and grandchildren will see fragments of asteroids, Mars and, hopefully, other planets returned when they visit museums.”
Two teams report study of Hayabusa2 asteroid samples More information: Tetsuya Yokoyama et al, Returned samples of Ryugu asteroid are similar to Ivuna-type carbonaceous meteorites, Science (2022). DOI: 10.1126 / science.abn7850
More information about Hayabusa2 on the JAXA website.
Provided by the University of Chicago
Citation: Scientists publish the first analysis of rocks taken from an asteroid at high speed …