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Asteroid Ryugu contains darkest material in the known solar system

Only five other meteorites similar to Ryugu have ever come to Earth

Adam Smith
Tuesday 21 December 2021 10:49

The asteroid Ryugu has some of the darkest and oldest material in our solar system, according to analysis of the cosmic object.

Samples from the asteroid were extracted in 2019 by Japan’s Hayabusa 2 probe, travelling more than 300 million kilometres from Earth and spending over a year on the rock to collect them.

Scientists at the time hoped that data collected from material under the asteroid’s surface could reveal information about the universe’s condition 46 billion years ago – especially with regards to how organic materials may be distributed across other planets in our galactic neighbourhood.

"It’s not just rare, it’s a very precious sample," Professor Masaki Fujimoto, who led the team that retrieved the Ryugu capsule, told ABC.

"It will tell us about the very early history of the solar system, and the process that made Earth habitable."

The 5.4 grams of material taken from the surface contain many unusual compounds, including organic and water-bearing molecules, New Scientist reports.

“Although most of these compounds are minor in terms of quantity – a few per cent at maximum – they have a high potential in tracing some of the processes that occurred in the earlier stages of the formation of the solar system and, later on, Ryugu’s parent body,” said Cédric Pilorget, an associate professor at the Institute of Space Astrophysics University of Paris-Saclay.

Scientists used techniques that would preserve the integrity of the asteroid, like hyperspectral microscopes that capture hundreds of images using light at different wavelengths.

However, the researchers found that the Ryugu sample was notably dark – much more so than other meteorites that we have studied – as it only reflected around two per cent of the light that hit it.

This suggests either that Ryugu has a different chemical makeup or that its journey through Earth’s atmosphere brightens meteors as they go through it.

Unlike other asteroids, the Ryugu sample also had a fine texture and did not contain any of the melted minerals – called chondrules – that scientists expected.

This suggests that the asteroid is the parent body of a rare type of meterorite called a CI chondrite – of which only five have ever made their way to Earth because of how easily they disintegrate in water. The chemical compositions of these meteorites is similar to a gasless Sun.

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