Asteroid Ryugu is definitely from outside the solar system

Scientists around the world are delighted with the results obtained from a 5.4-gram rock sample of the asteroid known as Ryugu. It’s not an ordinary sloppy at all.

Dirt was brought from the asteroid on the Hayabusa2 spacecraft and landed in the sands of South Australia nearly two years ago. It has provided researchers with unprecedented insights into the history of our solar system.

The space dust sample is the culmination of a six-year, 5 billion kilometer journey, and has now been analyzed by an international team of more than 200 researchers. They used ultra-bright X-rays, and found inside the rock, tiny impurities of water with carbon dioxide inside.

The researchers say this is further evidence that Ryugu’s parent body formed in the outer solar system, just two million years after the solar system began to form.

“There is sufficient evidence that Ryugu began in the outer solar system,” says Essen Alp, a physicist at the Argonne National Laboratory.

“Asteroids in the outer reaches of the solar system have different properties than those near the sun.”

“For planetary scientists, this is first-class information that comes directly from the solar system, and therefore is invaluable.”

At its closest orbit, Ryugu is only a quarter of the way from the Earth’s moon, which may indicate that the asteroid could have formed in the inner solar system.

However, this research, and a study conducted earlier this year in support of this finding, seem to indicate otherwise.

The team explained that the grains that make up the asteroid are much finer than you would expect if it formed at higher temperatures closer to the sun.

READ MORE: Ryugu asteroid samples shipped to South Australia contain extremely rare space dust

Earlier this year, researchers determined that the structure was incredibly similar to a rare type of asteroid from the outer solar system called CI chondrites.

“We’ve had other samples that came back from other planetary bodies before, but it was never the most primitive material in the solar system,” Professor Gretchen Benedix, an astronomer at Curtin University, explained at the time.

“On Earth we have 70,000 meteorites (we know they exist) – of which only nine are CI rated.”

These asteroids are supposed to form in the outer asteroid belt, more than four times the distance to Earth. This is because “4 AU” has crossed the “snow line” where the temperature is so low that all the water spontaneously freezes, but also cold enough for volatile components such as CO2 to condense into these ice grains.

These asteroids are also more abundant in evidence of the presence of organic molecules and water in those small inclusions. Think of inclusions as holes inside the sponge, rather than actual “drops” of water.

“Take the hydrogen and helium from the sun and what you have is a CI chondrite,” said Phil Bland, director of the Center for Space Science and Technology at Curtin University.

‚ÄúSince most of the mass of the solar system is in the sun, if you want to pick a combination of things that are average in the solar system, it’s the CI chondrite. It’s what it’s all made of.”

Thanks to the precise spectroscopy capabilities of a machine called the Advanced Photon Source, the new team was able to measure how much oxidation the samples had undergone. This was particularly interesting because the fragments themselves were never exposed to oxygen – they were delivered in airtight containers, in the primitive state of their journey through space.

The team also discovered something that distinguishes the Ryugu fragments from other CI chondrites – a large amount of iron sulfide called pyrrhotite. This finding also helps scientists put an end to the temperature and location of the original asteroid Ryugu at the time of its formation.

“Our results and those obtained from other teams show that the samples from these asteroids are different from meteorites, especially because meteorites were through fiery atmospheric entry, atmospheric conditions, and especially oxidation on Earth,” said Michael Ho, a physicist at Argonne National Laboratory.

“That’s exciting because it’s a completely different kind of sample, from the outside in the solar system.”

The search was published in Sciences.

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