The Ryugu asteroid can help us learn about how the solar system formed

According to estimates, our solar system is 4.57 billion years old. According to examinations of ancient meteorites, the minerals were produced through chemical reactions with water as far back as 4.5 billion years ago.

Astronomers and their colleagues at the University of California, Los Angeles, use mineral samples from… Ryugu The asteroid, collected by the Japanese spacecraft Hayabusa2, to better understand the chemical composition of our solar system when it was still in its infancy, more than 4.5 billion years ago.

In a new study, scientists used isotope analysis. They discovered that carbonate minerals from the asteroid crystallized through reactions with water, which originally accumulated on the asteroid as ice in the still-forming asteroid. Solar Systemand then heated to a liquid.

They assert that these carbonates evolved exceptionally early in the solar system’s history, during the first 1.8 million years, and that they serve as a record of the temperature and chemical composition of the asteroid’s liquid water at that time.

Study co-author Kevin McKeegan, professor of Earth, planetary and space sciences at UCLA, said, “The rocky, carbon-rich Ryugu is the first C-type asteroid (C stands for ‘carbonaceous’) from which samples have been collected and studied. What makes Ryugu special, is that unlike meteorites, it has had no possible contact with Earth. By analyzing the chemical signatures in the samples Scientists can develop a picture of not only how Ryugu formed but where.”

“The Ryugu samples tell us that the asteroid and similar objects formed relatively quickly in the outer solar system, outside fronts of water and carbon dioxide condensation, possibly as small bodies.”

Ryugu, or progenitor asteroid from which it may have broken off, it accumulated as a relatively small body, perhaps less than 20 kilometers (12.5 miles) in diameter. The researchers’ investigation revealed that the Ryugu carbonate originated several million years earlier than previously assumed.

The results surprised the researchers because most asteroid accumulation models would predict aggregation at longer periods, creating objects at least 50 kilometers (more than 30 miles) in diameter that could better survive collision evolution over the Sun’s long history. the system.

The researchers note, “Any larger asteroid that forms very early in the solar system may be heated to high temperatures due to the decay of large amounts of aluminum-26, a radionuclide, which leads to melting of rocks throughout the interior of the asteroid, along with chemical differentiation, such as segregation.” between metal and silicates.

Ryugu shows no evidence of this, and its chemical and mineralogical composition is equivalent to that of more chemically primitive meteorites, the so-called CI chondrites, which are also thought to have formed in the outer solar system.

mckegan said, “Ongoing research on Ryugu materials will continue to open a window on the formation of the solar system’s planets, including Earth.”

“Improving our understanding of volatile, carbon-rich asteroids helps us address important questions in astrobiology – for example, the possibility that rocky planets such as terrestrial ones could access a source of vital raw materials.”

So far, for the carbonates in the Ryugu samples, the team has extended the methodology developed in University of California to a different “short-lived” radioactive decay system involving the manganese-53 isotope, which was located in Ryugu.

Journal reference

  1. McCain KA, Matsuda N, Liu MC. et al. Early fluid activity on Ryugu has been inferred by isotopic analyzes of carbonates and magnetite. Nat Astron (2023). DOI: 10.1038 / s41550-022-01863-0

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