Scientists around the world are delighted with the results of the 5.4 gram rock sample of the asteroid known as “Ryugu”. It is absolutely not normal dirt.
The dirt was brought back from the asteroid to the Hayabusa2 spacecraft and landed in the sands of South Australia nearly two years ago. It allowed researchers to gain 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 over 200 researchers. They used ultra-bright X-ray beams, finding tiny “inclusions” of water with carbon dioxide inside the rock.
The researchers say this is further evidence that Ryugu’s parent body formed in the outer Solar System, just 2 million years after the Solar System began to form.
“There is sufficient evidence that Ryugu began in the outer solar system,” says Argonne National Laboratory physicist Esen Alp.
“The asteroids found in the outer reaches of the Solar System would have different characteristics than those closest to the Sun”.
“For planetary scientists, this is first-rate information coming directly from the Solar System, and therefore it is invaluable.”
In its closest orbit, Ryugu is only a quarter of the distance from the Moon’s Earth, which could suggest that the asteroid would have formed in the inner Solar System.
However, this research, and an earlier this year study supporting this finding, seem to suggest otherwise.
The team explains that the grains that make up the asteroid are much finer than would be expected if it formed at higher temperatures found closer to the sun.
Read More: Ryugu Asteroid Samples Shipped to South Australia Contain Super Rare Space Dirt
Earlier this year, the researchers determined that the structure was strikingly similar to a rare type of asteroid in the outer solar system called CI chondrites.
“We have had other samples from other planetary bodies before, but never the most primitive material in the Solar System,” explained Curtin University astrogeologist Gretchen Benedix at the time.
“We have 70,000 meteorites on earth (of which we know) – of these, only nine are classified as CI.”
These asteroids are assumed to form in the outer belt of the asteroids, more than four times the size of Earth. This is because “4 AU” is beyond the “snow line” where the temperature is so low that all the water will freeze automatically, but it is also cold enough to allow volatile components such as CO2 to condense into these grains of ice.
These asteroids are also more abundant in evidence than organic molecules and water in those small inclusions. Think of inclusions like holes inside a sponge, rather than real “drops” of water.
“You take hydrogen and helium from the sun and what you have is a CI chondrite,” said Phil Bland, director of the Space Science and Technology Center at Curtin University.
“Since most of the mass of the Solar System is in the Sun, if you want to choose a composition for the average material of the Solar System, it is chondrite CI. It is what it has all been 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 particularly interesting as the fragments themselves had never been exposed to oxygen – they were delivered in vacuum sealed containers, in pristine condition from their space travel.
The team also discovered something that distinguishes Ryugu fragments from other CI chondrites: a large amount of an iron sulfide called pyrrhotite. This finding also helps scientists to limit the temperature and position 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, particularly because meteorites have undergone entry into the fiery atmosphere, weathering and in particular oxidation on Earth,” he said. Argonne National Laboratory physicist Michael Hu.
“This is exciting because it’s a completely different kind of sample from the solar system.”
The research was published in Science.