The asteroid Ryugu contains some of the most primitive material ever studied in a laboratory on Earth, dating back only 5 million years after the formation of the solar system, according to an analysis of samples recovered by the Japanese Hayabusa2 mission.
Because it is so ancient, it is made of the same matter that formed the planets. “Ryugu is one of the building blocks of Earth,” team member Hisayoshi Yurimoto, a professor at Hokkaido University in Japan, told Space.com.
Japan Aerospace Exploration Agency Hayabusa2 the spacecraft was launched in December 2014 and arrived at the asteroid Ryugu in 2019. He recovered two small samples of regolith, worth 5.4 grams, from the asteroid. So these samples landed on Earth in a capsule equipped with a parachute in December 2020.
Related: Sample return mission of the asteroid Ryugu Hayabusa2 from Japan in pictures
Upon his return, the samples were distributed among scientific groups, including a team led by Tetsuya Yokoyama, a professor at the Tokyo Institute of Technology. The team’s recently published results suggest that the composition of the samples is the one that most closely matches the solar nebula: the cloud of gas that condensed to form the ground and planets, never found. As such, it is made up of the ingredients that formed the solar system 4.5 billion years ago.
The findings are supportive prior research this also concluded that Ryugu was made of primitive material, but until now it was not known how old he was.
Ryugu is a carbonaceous chondrite, that is, it is made of carbon-rich stony material. But Hayabusa2’s remote observations found some inexplicable discrepancies, such as a darker surface color, a greater abundance of phyllosilicate materials, and a more porous composition than expected, so a laboratory analysis was required to better understand the asteroidtrue nature. Ryugu is somewhat similar to the meteorite Ivuna, which fell in Tanzania in 1938 and was loaned by the Natural History Museum in London to the Yokoyama team for study.
“The comparison between Ivuna and Ryugu is very helpful in revealing Ryugu’s characteristics,” Yurimoto said.
Using a variety of techniques, such as electron microscopy, X-ray fluorescence, inductively coupled plasma mass spectrometry, and thermal ionization, the team found that the samples had formed in liquid water at a temperature of between 27 and 47 degrees Fahrenheit. degrees Celsius), about 5 million years after the solar system began to form.
JAXA staff inspects Hayabusa2’s return capsule against red soil in the Woomera Prohibited Area in Australia on 5 December. (Image credit: JAXA)
At only 3,000 feet (900 meters) in diameter, Ryugu is too small to have generated enough heat to melt the ice water. Therefore, Ryugu itself must have originated from a larger parent body that formed only 2 to 4 million years after the birth of the solar system. At some point after 5 million years, a powerful one impact with another asteroid he broke Ryugu’s ancestral body, with some of the fragments forming Ryugu. This idea is supported by the presence of large blocks on the surface of Ryuguwhich appear to have originated as debris from a giant impact.
Ryugu material can be dated thanks to the abundance of certain elements (hydrogen and noble gases) within the samples. They are the closest coincidence we have to the composition of the visible surface of the sun, the photospherewhich is used as a proxy for the composition of the solar nebula.
No meteorite or asteroid material has been studied in a laboratory Earth she has never been so primitive and virgin. Some meteorites, such as Ivuna, may have once been so pristine. But after being on Earth for decades, if not centuries, where they were exposed to atmospheric humidity and weather, and then manipulated by humans, their mineralogies and elemental composition may have been compromised.
A key question that needs to be answered to fully explain the origin of the planets is where the smaller bodies, such as asteroids and comets, some of which became planetary building blocks, were formed. Their compositions suggest that many of these bodies did not form in their current orbits and that in the chaotic early solar systemwith their turbulent protoplanetary disk and migrating planets, the smaller bodies were pushed and away from where they formed.
Knowing when Ryugu’s parent body was formed and that it contained water, can we tell where the asteroid must have formed?
“This is a very difficult question,” Yurimoto said. “We have no quantitative answer, but it would be beyond the snow line of the solar system, [which is] located in the orbit of Jupiter. “(The snow line is the distance from the sun where the ice water could have condensed during the formation of the solar system.)
This is just the beginning of the analysis of samples taken home by Hayabusa2. The next step is to use the information contained in these samples to determine the abundance of various elements and their isotopes in the first solar system when the planets formed. According to Yurimoto, once determined, these abundances “would become a new standard for studies of the solar system.”
The findings are published in the June 9 issue of the journal Science.
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