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Boffins' first take on asteroid dust from Japanese probe: Carbon rich, less lumpy than expected

The five grams of Ryugu we got suggests it's made of the same stuff as the outer Sun

Researchers have published the first analyses of samples plucked from asteroid 162173 Ryugu by Japan's spacecraft Hayabusa2, revealing, for the first time, the physical properties and composition of a carbonaceous asteroid.

The 5.4g of asteroid sample collected from two surface locations on asteroid Ryugu landed in the South Australian outback a year ago before being shipped to Japan for investigation.

Some of the space pebbles went to NASA, but the bulk remained with Japan's Aerospace Exploration Agency JAXA and its scientists.

Astro-boffins have had high hopes for these samples, as they’ve never before had their hand on a dark and carbon-rich asteroid, or C-type, like Ryugu.

Studies of the samples physical properties revealed the sample resembled the spacecraft’s on-site images of the flying space-rock and the collected material was representative of the asteroid as a whole.

Rich in water and organic matter, the ultra-dark material was a mix of elements rarely seen in meteorites that make it down to Earth, despite these C-type asteroids being the most common in the Solar System. The texture was also unusual, as it was uniformly fine and did not include the round chunky bits of melted minerals known as "chondrules".

Those characteristic suggest that Ryugu's parent body was a CI chondrite, a rare meterorite with a composition close to the stuff found in the Sun’s outer shell.

“This demonstrates that Hayabusa2 has returned a sample whose parent body is definitively known and which will give us information about the early stages of the Solar System,” said the authors of one of two papers published on Ryugu Tuesday in the journal Nature Astronomy. The authors made that assertion as the composition of CI chondrites are similar to the stuff theorized to have made up much of the Solar System when it was just formed.

The results are exciting for supporters of the panspermia theory, which proposes that the building blocks for life are transported across the cosmos via comet or asteroid. C-type asteroids, in particular are thought to have seeded a young Earth with water and other essential life-supporting materials. Indeed, scientists found organic molecules on the first comet humanity intercepted, Comet 67P/Churyumov-Gerasimenko. There’s no reason known why chunks of comets housing organic materials wouldn’t survive an impact and spread their cargo far and wide.

Of course, beyond the philosophical questions about humanity’s maker, there’s also a very real reason to study asteroids and that is that it would be really great to avoid having one hit the Earth and end all the fun and games here.

Scientists continue to dig in to the Ryugu samples and hope follow up studies might tell us how the Solar System evolved. Comparisons of Ryugu to other asteroids are planned, to test for variations.

In addition to the dust and pebbles, the mission also produced what JAXA referred to as “the world's first sample return of a material in the gas state from deep space,” so we have more to look forward to than just solid matter. ®

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