HomeScienceOuter SpaceAsteroid Ryugu sure of the outer solar system

Asteroid Ryugu sure of the outer solar system

Scientists around the world are excited about the findings of the 5.4 gram rock from the asteroid known as “Ryugu”. It is definitely not ordinary dirt.

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

The monster of space dust is the pinnacle of a journey of six years and 5 billion kilometers, and has now been analyzed by an international team of more than 200 researchers. They used ultra-bright X-rays and found small ‘inclusions’ of water containing carbon dioxide in the rock.

The researchers say this is more evidence that Ryugu’s parent body formed in the outer solar system, just 2 million years after the solar system started forming.

“There is plenty of evidence that Ryugu started in the outer solar system”, Argonne National Laboratory physicist Esen Alp says.

“Asteroids found in the outer reaches of the solar system would have different characteristics than those closer to the sun.”

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

At its closest orbit, Ryugu is only a quarter of the distance from Earth from the moon, suggesting that the asteroid formed in the inner solar system.

However, this research, and a study from earlier this year that supports this findingseems to suggest otherwise.

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

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Read more: Ryugu asteroid samples dropped to South Australia contain super-rare space debris

Earlier this yearresearchers found that the structure was incredibly similar to a rare type of asteroid from the outer solar system called CI-chondrites.

“We’ve gotten other samples from other planetary bodies before, but never the most primitive material in the solar system,” Curtin University astrogeologist Prof Gretchen Benedix explained at the time.

“On Earth, we have 70,000 meteorites (as far as we know) — of these, only nine are classified as CI.”

These asteroids are believed to form in the outer asteroid belt, more than four times the distance from Earth. This is because ‘4’ ouch‘ is beyond the ‘snowline’ where the temperature is so low that all water freezes automatically, but it is also cold enough for volatile components like CO2 to condense in these ice grains.

These asteroids are also more abundant in evidence of organic molecules and water in those tiny inclusions. Think of inclusions like the holes in a sponge, rather than actual ‘drops’ of water.

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

“Since most of the solar system’s mass is in the sun, it’s CI chondrite if you want to pick a composition for average solar system stuff. That’s what everything is made of.”

With the finely tuned spectroscopy capabilities of a machine called the Advanced Photon Source, the new team was able to measure the amount of oxidation the samples had undergone. This was especially interesting because the fragments themselves had never been exposed to oxygen – they were delivered in vacuum-sealed containers, in pristine condition from their journey through space.

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The team also discovered something that differentiated the Ryugu fragments from other CI chondrites: a large amount of iron sulfide called pyrrhotite. This result also helps scientists put a limit on the temperature and location of Ryugu’s parent asteroid at the time it formed.

“Our results and those of other teams show that these asteroid samples are different from meteorites, mainly because meteorites have invaded a fiery atmosphere, undergone weathering and, in particular, oxidation on Earth,” said Argonne National Laboratory physicist Michael Hu.​

“This is exciting because it’s a very different kind of monster from far away in the solar system.”

The research was published in Science.



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