The rock brought back from an asteroid is so old that it predated the solar system.
A new analysis of samples of asteroidryugu has shown the presence of mineral grains forged in the outflows of old stars before our own Sun formed.
The Ivuna-type carbonaceous (CI) chondrites are very similar to the Ryugu meteorite. The presence of some fragile grains indicates that parts of the asteroid may not have changed.
Presolar stardust grains were found in the samples returned from asteroidryugu. They are similar to presolar material found in CIchondrites. The researchers wrote in their paper that their results show that asteroid Ryugu is related to CIchondrites.
The small regions ofRyugu allowed their preservation.
The preservation of the isotope ratios in presolar grains makes them very valuable as snapshots of processes that occur in distant stars; as such, they are a direct record of those stars and their chemistry. They can be used to understand the evolution of stars other than the Sun.
There are very few presolar grains. The majority of meteorites that fall to Earth are found in carbonaceous chondrites. Around 5 percent of carbonaceous chondrites have been found to have presolar grains. The oldest one to date is between 5 and 7 billion years old.
There are some presolar grains in the material. The international team led by Jens Barosch of the Carnegie Institute of Washington found 57 grains with presolar isotope ratios.
The team compared the grains with meteorites and found that they were very similar to CIchondrites. The most similar chemical composition to the Sun seen in meteorites is found in these.
The mineralogy of the samples shows that water-rock interactions on the parent body have caused extensive alterations. One of the grains discovered by the team is a pre solar silicate. This finding was particularly unexpected since silicates are easy to destroy.
Presolar silicates can only be found in relatively rare sections of the rock that are less altered than the overall matrix. These clasts are able to preserve delicate grains.
The researchers say that similar water-free clasts in other CI meteorites could reveal other delicate presolar grains.
The presence or absence of presolar material in these clasts would provide important clues about their origin and their history of secondary processing.
The systematic searches for presolar grains will provide a representative data set of presolar grain abundances and characteristics in asteroidryugu and will give the maximum scientific information from these precious samples.
The research has appeared in a journal.
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