Scientists said on Thursday that one-fifth of an ounce of dark spots carried from an asteroid to Earth by a Japanese spacecraft are some of the most pristine fragments of the baby’s solar system studied so far. Was announced.
That fact should help planetary scientists refine their knowledge of the components of the dust and gas discs that orbited the Sun about 4.6 billion years ago before they merged into planets and smaller bodies.
“We have to rewrite the chemistry of the solar system,” said Hisayoshi Yurimoto, a professor of earth and planetary sciences at Hokkaido University in Japan and responsible for research analysis. Papers published by Journal Science On thursday.
The Hayabusa2 spacecraft arrived at Ryugu, a carbon-rich asteroid, in 2018. The mission was run by JAXA, Japan Aerospace Exploration Agency, and spent more than a year researching Ryugu. This included a short descent to the surface several times to pick up a sample of dirt from the asteroid, or even exploding a new crater on the surface using an explosive.
In December 2020, Hayabusa2 passed through the Earth again and dropped a small capsule containing a small piece of Ryugu in the interior of Australia.
Mission scientists spent last year studying what Hayabusa2 brought back. “It’s a mountain of rocks, pebbles, and sand,” said Shogo Tachibana, a planetary scientist at the University of Tokyo who is in charge of sample analysis. He said the biggest piece was about a centimeter in size, about four tenths of an inch. Many of the particles were about 1 millimeter wide.
Dr. Yurimoto’s team received only a small amount of asteroids — less than 1/200 of an ounce.
The greatest surprise from their analysis is that the fragments of Ryugu are in close agreement with the 1.5-pound meteorite that landed in Tanzania in 1938. The Ivena meteorite, named after the area where it fell, was a very rare type. Of the more than 1,000 cosmic rocks found on the surface of the Earth, only five of this type, known as CI chondrites.
(C stands for carbonaceous, which means it contains carbon compounds, I stands for Ivuna, and chondrites are stony meteorites.)
“It’s very similar,” said Bennu, another carbon-rich asteroid, leader of the Planetary Materials Group at the Natural History Museum in London, a member of the OSIRIS-REX science team on the Hayabusa2 and NASA missions. .. She was the author of the science paper.
A sample of OSIRIS-REX from Bennu will return to Earth next year.
Dating of Ryugu samples showed that the material was formed about 5.2 million years after the birth of the solar system.
Dr. Russell said carbonaceous chondrites are believed to have formed in the outer parts of the solar system, farther than the current orbits of most asteroids. She described them as “basically deeply frozen relics from the early solar system.”
CI meteorites have a heavy elemental composition that is very similar to that measured on the surface of the Sun, such as the ratio of sodium to sulfur to calcium. Therefore, planetary scientists considered these to be good signs of the building blocks that filled the early solar system. It provides important parameters for computer models aimed at understanding how planets were formed.
Analysis showed that the material was heated early in its history, melting ice into water, which triggered a chemical reaction that changed the minerals. However, the relative amounts of the various elements remained largely unchanged, scientists said.
It matches the painting formed from the rubble that Ryugu knocked off the asteroid Mile, which is much larger in diameter. (The CI meteorite probably came from a larger parent asteroid, not Ryugu.)
The results were “very important,” said Victoria Hamilton, a scientist at the Southwest Institute in Boulder, Colorado, who was not involved in the study. “We learned a lot about the early solar system from meteorites here on Earth, but they lack any kind of context.”
In this case, the planetary scientist knows exactly where the sample came from.
The match between Ryugu and CI meteorite was unexpected. This is because the CI meteorite contains a lot of water, and telemetry of Hayabusa2 on Ryugu showed the presence of some water, but the surface was almost dry. However, laboratory measurements revealed about 7% water content, says Dr. Tachibana, co-author of a new scientific study. That is a considerable amount for such minerals.
Dr. Tachibana said scientists are working to understand the contradictions.
Scientists have also found some differences between the Ryugu sample and the Evna meteorite. The Evna meteorite contained even more water, a mineral called sulfate that did not exist on Ryugu.
This difference may show how meteorite mineralogy has changed over the decades of sitting on Earth, absorbing water from the atmosphere and undergoing chemical reactions. This could help scientists understand what was formed as part of the solar system 4.6 billion years ago and what has recently changed in CI meteorites over decades on Earth.
“This shows why it’s important to go on space missions, go out, explore and bring back materials in a truly controlled way,” Dr. Russell said.
This also raises expectations for the OSIRIS-REX Bennu sample, which will land in the Utah Desert on September 24, 2023. The mission’s lead researcher, Dantella Uretta, showed that OSIRIS-REX measurements at the asteroid CI, and Bennu, showed more water than Hayabusa2 observed at Ryugu. However, if Ryugu is already consistent with the CI meteorite, it suggests that Bennu may be made of something else.
“So now I’m wondering what to bring back,” said Dr. Lauretta, the author of the science paper. “It’s kind of exciting, but it’s also intellectually challenging.”