Asteroid Ryugu formed in the outer solar system before approaching Earth

(ORDO NEWS) — Asteroid Ryugu is one of the most famous near- Earth objects . A few years ago, it was visited by the Japan Aerospace Exploration Agency (JAXA) Hayabusa-2 spacecraft, which collected samples from the surface and from under it, and then delivered them to Earth.

Initial analysis of the samples provided incredible information about Ryugu, and subsequent studies have continued this trend. For example, Ryugu’s association with comet Wild 2 (81P/Wild or Wild 2) and the outer solar system has recently been discovered.

On January 2, 2004, Comet Wild 2 was visited by NASA‘s Stardust spacecraft, which collected tiny particles from the comet’s coma, a rarefied cloud of gas and dust that forms when a comet approaches the Sun.

Thanks to this mission, we know that Wild 2 was formed far in the outer solar system, but in September 1974, after passing very close to Jupiter, it was “catapulted” into the inner solar system.

Ryugu – the mystery of the solar system

Ryugu’s story seems to be more complex. An analysis published earlier this year identified amino acids (the building blocks of macromolecules called proteins) as well as carbonate minerals expected to form in water-rich environments at low temperatures.

This suggests that Ryugu’s birthplace could not have been the inner solar system. In addition, Ryugu showed similarities with the Iwuna meteorite, which fell in Tanzania on December 16, 1938 and is part of the CI-chondrite group.

To date, only nine CI chondrites are known, so this class of asteroids is one of the rarest.

Chemical analysis of the isotopic composition of copper and zinc in both Ryugu and Yiwun again shows a surprising similarity.

Recall that isotopes are versions of the same chemical element with different masses due to the presence of additional neutrons in the nucleus.

This chemical fingerprint provides very intriguing information about the composition and history of the formation of space rocks.

Asteroid Ryugu formed in the outer solar system before approaching Earth 2
The surface of Ryugu, captured as part of the Hayabusa-2 mission

Ryugu contains some materials that could not have formed in the outer solar system. Minerals such as olivine, spinel and perovskite are formed at high temperatures.

And the isotopic signatures of oxygen-16 in these minerals show that some of them are saturated with this oxygen isotope, while others are not.

But this ratio is very similar to the ratio in CI chondrites, but differs from the ratio in carbonaceous meteorites.

And what’s also very interesting is that this ratio is also similar to the comet dust collected in the coma of Wild 2, which is another important link between Ryugu and the outer solar system.

Evidence suggests that asteroid Ryugu and CI chondrites formed closer to the region where comets accrete material.

But those minerals that need high temperatures to form formed in the inner solar protoplanetary disk and were moved outward before space bodies moved closer to Earth.

In other words, Ryugu – and similar objects – is a mixture of materials that appeared in different regions of the solar system.


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