A year ago, scientists got their first look at material collected from the nearby asteroid 162173 Ryugu. Now the results of these studies have been revealed, and they have shed light on the history of our solar system and the long journey of this cosmic wanderer.
At its closest orbit, asteroid 162173 Ryugu is only about 60,000 miles from Earth. This is only a quarter of the distance to the moon. But according to newly released results from an international team of scientists, this rocky massif began its cosmic journey more than 4 billion years ago, billions of miles away, in the outer part of our solar system. He has traveled to us through space, taking into account the history of this corner of the universe in the process.
These discoveries are only part of the results of a global effort to study samples from the surface of Ryugu. These asteroid dust patches were carefully collected and transported back to Earth by Hayabusa 2, a mission operated by the Japanese space agency JAXA, and then sent to institutions around the world. Scientists put these tiny fragments through dozens of experiments to elicit their secrets, to determine what they are made of and how the asteroid they came from might have formed.
“For planetary scientists, this is first-class information that comes directly from the solar system, and therefore is invaluable.” – Esen Erkan Alp, Argun’s special teammate
The resulting paper, recently Posted in Sciences, featuring authors from more than 100 institutions in 11 countries. Among them is the US Department of Energy’s (DOE) Argonne National Laboratory, which is home to the Advanced Photon Source (APS), a user facility of the Department of Energy’s Office of Science. APS generates ultra-bright X-rays that can be used to determine the chemical and structural composition of atom-by-atom samples.
Argonne Esen Distinguished Fellow Ercan Alp led the Argonne research team, which includes physicist and group leader Jiyong Zhao and physicist Michael Hu, and Barbara Lavina from both Argonne and the University of Chicago. They are all co-authors of the paper.
Alp and his team worked for years to be included in this study. Alp said that APS’s main contribution is a special X-ray technology that he and his team specialize in. It’s called Mössbauer spectroscopy – named after German physicist Rudolf Mössbauer – and is very sensitive to small changes in the chemistry of samples. This technique allowed Alp and his team to determine the chemical composition of these parts of a particle.
What they and their international colleagues found was surprising, Alp said.
“There is sufficient evidence that Ryugu began in the outer solar system,” he said. “Asteroids in the outer reaches of the solar system have different properties than those near the sun.”
Alp said APS found several evidence to support this hypothesis. First, the grains that make up the asteroid are much finer than you would expect if it formed at higher temperatures. On the other hand, the structure of the fragments is porous, which means that they previously contained water and ice. Albee said that cooler temperatures and ice are more common in the outer solar system.
Ryugu fragments are very small – around 400 microns, or the size of six human hairs, and 1 millimeter in diameter. But the X-ray beam used in 3-ID-B beam line can be focused down to 15 microns. The team was able to take several measurements on each of the fragments. They found the same porous and fine-grained structure across the samples.
Thanks to the finely tuned spectroscopy capabilities of APS, the team was able to measure how much oxidation the samples had undergone. This was particularly interesting because the fragments themselves were never exposed to oxygen – they were delivered in airtight containers, in the primitive state of their journey through space.
While the APS team found chemical make-up similar to meteorites that struck Earth – specifically a group of them called CI chondrites, only nine of which are known to exist on the planet – they discovered something that characterizes the Ryugu fragments.
Spectroscopic measurements found a large amount of peridotite, an iron sulfide that is not found anywhere in the scores of meteorites that the team also studied, courtesy of French collaborators Mathieu Roscoeuse (National Museum of Natural History) and Pierre Beck (University of Grenoble Alpes). This finding also helps scientists put an end to the temperature and location of the original asteroid Ryugu at the time of its formation.
“Our results and those obtained from other teams show that these asteroid samples are different from meteorites, especially because meteorites were through entering the fiery atmosphere, weather and especially oxidation on Earth,” Hu said. “That’s exciting because it’s a completely different kind of sample, from the outside in the solar system.”
With all the data combined, the paper identifies the 162,173 Ryugu date to be several billion years old. It was once part of a much larger asteroid that formed about two million years after the formation of the solar system – about 4.5 billion years ago. It was made of many different materials, including water ice and carbon dioxide, and over the next three million years, the ice melted. This dampened the interior and the surface, which was dry.
About a billion years ago, another piece of space rock collided with this asteroid, shattering it and flying debris, and some of these fragments collected in the asteroid Ryugu that we know today.
“For planetary scientists, this is first-class information that comes directly from the solar system, and therefore it is invaluable,” Alp said.
Argonne’s team plans their own paper, going into detail about X-ray techniques and their results. But they said being part of this large, multinational scientific effort was exciting, and they look forward to being part of future experiments of this kind.
“This has been an exciting and challenging experience for us to participate in such a well-coordinated international research project.” Zhao said. “with Upgrade to APS in the works which will provide brighter X-rays, we expect to study more materials like this, from asteroids and distant planets. “
This project was partially funded by a grant from France and Chicago collaborate in science (FACCTS), operated by the University of Chicago.
About the advanced photon source
The US Department of Energy’s (APS) Advanced Photon Source at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. APS provides high-brightness X-rays to a diverse community of researchers in materials science, chemistry, condensed matter physics, life sciences, the environment, and applied research. These X-rays are ideally suited for the exploration of biological materials and structures; the distribution of the elemental chemical, magnetic and electronic states; and a wide range of technologically important engineering systems from batteries To supply fuel injector nozzles, all of which are the basis of the economic, technological and material well-being of our nation. Each year, more than 5,000 researchers use APS to produce more than 2,000 publications detailing influential discoveries, solving more critical biological protein structures than any other research facility uses for an X-ray light source. APS scientists and engineers create technology that is at the heart of driving accelerators and light sources. This includes input devices that produce extremely bright X-rays that researchers value, lenses that focus X-rays down to a few nanometers, devices that increase the way X-rays interact with the samples being studied, and software that collects and manages the vast amount of data generated by discovery research in APS.
This research used Advanced Photon Source Resources, a US Department of Energy user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357.
Argonne National Laboratory It seeks to find solutions to pressing national problems in science and technology. Argonne, the country’s first national laboratory, conducts groundbreaking basic and applied scientific research in nearly every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state, and municipal agencies to help them solve their specific problems, advance American scientific leadership, and prepare the nation for a better future. With employees from more than 60 countries, Argonne is managed by UChicago Argonne, LLC to US Department of Energy Office of Science.
US Department of Energy Office of Science It is the largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information visit https://energy.gov/sc ience.
The formation and evolution of the carbonaceous asteroid Ryugu: direct evidence from returned samples
The date the article was published
September 22 2022