Minerals in Ryugu formed at the dawn of the Solar System

Jan. 19 () –

Analysis of samples brought back from the Ryugu asteroid indicate that carbonates formed from water-rock reactions that occurred very shortly after the beginning of the Solar System.

It is estimated that our solar system is about 4,570 million years old. Previous analyzes of ancient meteorites had shown that the minerals were created by chemical reactions with water as early as 4.5 billion years ago. But the Ryugu samples push these reactions back millions of years.

In research published in nature astronomyUCLA (University of California Los Angeles) scientists discovered, through isotopic analysis, that carbonate minerals from the Ryugu asteroid crystallized by reaction with water, which originally adhered to the asteroid as ice in the solar system still forming and then heated to a liquid.

These carbonates, they say, formed very early -during the first 1.8 million years of the existence of the solar system- and they keep a record of the temperature and composition of the asteroid’s aqueous fluid as it existed at the time.

Ryugu, rocky and rich in carbon, It is the first C-type asteroid. (C stands for “carbonaceous”) from which samples have been collected and studied, explained Kevin McKeegan, study co-author and distinguished professor of Earth, Planetary and Space Sciences at UCLA. What makes Ryugu special, he pointed out, is that, unlike meteorites, it has not had potentially contaminating contact with Earth. By analyzing the chemical fingerprints of the samples, scientists can get an idea 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, beyond the condensation fronts of water ice and carbon dioxide, probably as small bodies,” McKeegan said. it’s a statement.

The researchers’ analysis determined that the Ryugu carbonates formed several million years earlier than previously thought, indicating that Ryugu—or a parent asteroid from which it may have broken off—clumped together as a relatively small object, probably less than 20 kilometers in diameter.

According to McKeegan, this result is surprisingsince most asteroid accretion models predict assembly over longer periods, giving rise to the formation of bodies at least 50 kilometers in diameter that could better survive the evolution of collisions along of the long history of the solar system.