Scientists release first analysis of rocks taken from high-speed asteroid

Left: A photograph of rocks recovered by Hayabusa2 from asteroid Ryugu. Right: an enlarged image of the structure of one of the parts, obtained by an electron microscope. Credit: JAXA/Yokoyama et al.

After a six-year journey, a courageous spacecraft called Hayabusa2 returned to Earth’s atmosphere in late 2020 and landed deep in the Australian outback. When researchers from the Japanese space agency JAXA opened it up, they found its precious payload sealed and intact: a handful of dirt Hayabusa2 managed to scrape off the surface of a speeding asteroid.

Scientists have now started announcing the first results of the analysis of this extraordinary sample. What they found suggests that this asteroid is a piece of the same material that coalesced into our sun four and a half billion years ago.

“Before, 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 to centuries, which changed their compositions,” said geochemist Nicolas Dauphas, one of three researchers at the University of Chicago researchers who worked with an international team of scientists led by Japan to analyze the fragments. “Having pristine samples from outer space is just amazing. They are witnesses to parts of the solar system that we haven’t explored otherwise.”

‘It’s spectacular’

In 2018, Hayabusa2 landed on top of a moving asteroid called Ryugu and collected particles 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 are eagerly awaiting the unique sample – one that could help redefine our understanding of how planets evolve and how our solar system formed.

Scientists are particularly excited that these particles would never have reached Earth without the protective barrier of a spacecraft.

“Usually all we have to study asteroids are pieces that are large enough to reach the ground as meteorites,” said UChicago geochemist Andrew M. Davis, another member of the analysis team. “If you take this handful and throw it into the atmosphere, it will burn. You will lose it, and a lot of evidence about the history of this asteroid will go with it.

“We haven’t really had a sample like this before. It’s spectacular.”

Cientistas divulgam primeira análise de rochas retiradas de asteroide em alta velocidadeScience (2022). DOI: 10.1126/science.abn7850″/>

Petrography of the Ryugu sample. (A) Backscattered electron (BSE) image of Ryugu sample A0058-C1001. The black space in the figure is a pore. (B) Combined elemental map of the same sample, with characteristic X-rays of the Ca Kα, Fe Kα and S Kα lines assigned to the RGB color channels as indicated in the legend. Carbonate (dolomite), sulphide (pyrrhotite) and iron oxide (magnetite) minerals are embedded in a matrix of phyllosilicates and, in some cases, precipitated in small veins. The sulfide texture is similar to that of Flensburg unclustered chondrite. (C) Ternary diagram between Fe, Mg and Si+Al showing the chemical compositions of the phyllosilicates in A0058-C1001. The black lines are solid solution compositions for serpentine and saponite. Each open red circle shows the chemical composition by mass of phyllosilicates measured at various locations in panels A and B, each location being a 5 to 10 μm square. We chose each size to exclude minerals other than phyllosilicates in the area. Volume compositions differ from place to place, with a distribution indicating that phyllosilicates consist of serpentine and saponite with varying Fe/Mg ratios. The uncertainties in each measurement are smaller than the symbol size. (D) BSE image of Ryugu sample C0002-C1001, showing the brecciated 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 assembled to help Japanese researchers analyze the samples. Every part of the capsule’s contents is being rigorously studied. Yokochi is part of a team that is analyzing the gases that have become trapped in the capsule or in the dirt. Dauphas and Davis are part of a team studying the chemical and isotopic compositions of grains to reveal their history.

The first compilation of these results, reported in Science on June 9, reveal Ryugu’s makeup.

The rock is similar to a class of meteorites known as “Ivuna-type carbonaceous chondrites”. These rocks have a similar chemical composition to what we measure from the sun and are believed to date back to the early days of the solar system, approximately four and a half billion years ago – before the formation of the sun, moon and moon. Earth. [should Moon be capitalized to distinguish it from other moons?]

At that time, all that existed was a gigantic cloud of rotating gas. Scientists think that most of this gas was pulled towards the center and formed the star we know as the sun. As the remnants of this gas expanded into a disk and cooled, they turned into rocks, which still float around the solar system today; looks like Ryugu might be one of them.

Scientists said the fragments show signs of having been soaked in water at some point. “One has to imagine an aggregate of ice and dust floating in space, which turned into a gigantic ball of mud when the ice was melted by nuclear energy from the decay of radioactive elements that were present in the asteroid when it formed,” he said. Dauphas But surprisingly, today the rock itself appears to be relatively dry.

Scientists release first analysis of rocks taken from high-speed asteroid

The surface of asteroid Ryugu from an altitude of 6 km. Credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST

Using radioisotope dating, they estimated that Ryugu was altered by the circulation of water only about five million years after the formation of the solar system.

These findings are particularly interesting to researchers because they suggest similar formation conditions between comets and some asteroids, such as Ryugu.

“By examining these samples, we can narrow down the temperatures and conditions that must have occurred in their lives and try to understand what happened,” explained Yokochi.

She likened the process to trying to figure out how a soup was made, but with only the end result and not the recipe: “We can take the soup and separate the ingredients, and try to tell by their conditions how much was in which order.”

Scientists noted that a percentage of the discovery will be set aside so that we can analyze them in the future with more advanced technology – just as we did with Apollo lunar samples.

“After we received lunar samples from Apollo 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 release first analysis of rocks taken from high-speed asteroid

Scientists from the Japanese Space Agency traveled to the Australian outback to retrieve the capsule containing pieces taken from the surface of a high-speed asteroid by the Hayabusa2 spacecraft in December 2020. Credit: JAXA

“The same will be true of these samples. This is a gift that keeps on giving.”

This mission is the first of several international missions that will sample another asteroid called Bennu, as well as unexplored areas on our moon, Mars, and Mars’ moon Phobos. All of this should happen in the next 10 to 20 years.

“It’s very much off the radar of the public and some decision makers, but we are entering a new era of planetary exploration unprecedented in history,” Dauphas said. “Our children and grandchildren will see asteroid fragments, Mars and hopefully other planets when they visit museums.”


Two teams report study of Hayabusa2 asteroid samples


More information:
Tetsuya Yokoyama et al, Samples returned from asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites, Science (2022). DOI: 10.1126/science.abn7850

Read more about Hayabusa2 on the JAXA website.

Provided by the University of Chicago

Quote: Scientists release first analysis of rocks taken from high-speed asteroid (2022, June 9) recovered June 10, 2022 from https://phys.org/news/2022-06-asteroid-samples-chance-chemically- pristine.html

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