The Ryugu asteroid holds a key to understanding the formation of the solar system

Samples from asteroid 162173 Ryugu collected by the Japanese spacecraft Hayabusa2 can help us understand the chemical composition of our solar system.

Discovered in 1999, Japanese scientists working on the Hayabusa2 spacecraft discovered the Ryugu asteroid known as 162173 Ryugu, which has a diameter of about 900 meters.

In this asteroid, ancient dust grains older than the solar system itself were found in samples brought back by the Japanese spacecraft Hayabusa2 nearly two years ago.

Now, UCLA scientists have revealed that minerals from the asteroid were produced through reactions with water more than 4.5 billion years ago – helping us to better understand the chemical makeup of our solar system as it existed in its infancy.

minerals over 4.5 billion years ago

Carbonate minerals from the asteroid crystallized with water

search in natural astronomy Using isotopic analysis, scientists explain that the carbonate minerals from the asteroid crystallized through reactions with water, which originally accumulated on the asteroid as ice in the still-forming solar system, then warmed into a liquid.

During the first 1.8 million years of the solar system’s existence, these carbonates formed – which is very early in the history of our solar system – and they keep a record of the temperature and chemical composition of the asteroid’s liquid water as it existed at that time.

Carbon-rich Ryugu is the first C-type asteroid (C stands for “carbonaceous”) from which samples were collected and studied, and which, unlike meteorites, did not contaminate its contact with Earth.

ASTEROID SURFACE RYUGU Image of the surface of Ryugu (162173), taken at night by the Asteroid Surface Scout Camera (MASCOT) from Hyabusa-2 MASCOT/DLR/JAXA

What does 162173 Ryugu look like?

By analyzing the chemical composition and fingerprints in the samples, scientists can develop a picture of not only how but where Ryugu formed.

“The Ryugu samples tell us that asteroids and similar objects formed relatively quickly in the outer solar system, outside fronts of water and carbon dioxide condensation, possibly as small bodies,” said Kevin McGeegan, Distinguished Professor of Earth, Planetary and Space Sciences at UCLA.

Through the research, they gathered that the Ryugu carbonate formed several million years earlier than previously thought, and indicated that Ryugu (or a predecessor asteroid from which it may have broken off) accreted as a relatively small body, perhaps less than 20 kilometers (12.5 miles) in diameter. .

Ryugu is likely from a small asteroid

162173 Ryugu is an anomaly in their research, in that most models of asteroid accumulation would predict aggregation at longer periods, creating objects at least 50 kilometers in diameter that could better survive collision evolution over the solar system’s long history.

“It is unlikely that it will ever be a large asteroid,” the researchers note.

“It is unlikely that it will ever be a large asteroid.”

Any larger asteroid forming very early in the solar system might be heated to high temperatures by the decay of large amounts of aluminum-26, a radionuclide, leading to melting of rocks throughout the asteroid’s interior, along with chemical differentiation, such as Metal and silicate insulation.

However, Ryugu offered no evidence for 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.

To date the carbonates in the Ryugu samples, the team extended the methodology developed at UCLA for a different “short-lived” radioactive decay system involving the manganese isotope 53, which was present in Ryugu.

Answering vital questions in astrobiology

“Improving our understanding of volatile, carbon-rich asteroids helps us address important questions in astrobiology — for example, the possibility that rocky planets like rocky planets could access a source of vital raw materials,” McKegan adds.

Ongoing research on Ryugu materials will continue to open a window on the formation of the Solar System’s planets, including Earth.

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