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First Comprehensive Analysis of Asteroid Bennu

The Osiris-Rex spacecraft successfully picked up the materials from an asteroid called Bennu in October 2020, 205 million miles from Earth. It then took almost three years for the NASA probe to come home and drop off its precious cargo in a Utah desert. That happened on 24 September last year. Now, what the probe contained is being revealed.

A close-up of NASA's OSIRIS-REx sample trays, containing dust and rubble plundered from asteroid Bennu
A close-up of NASA's OSIRIS-REx sample trays, containing dust and rubble plundered from asteroid Bennu | Credit: NASA/Erika Blumenfeld & Joseph Aebersold

Nearly four years after NASA's OSIRIS-Rex spacecraft collected the sample, scientists are finally revealing the intriguing composition of the space rock. And, unlike most meteorites, whose surfaces are altered by years-long exposure to Earth's air by the time they are found, pieces of Bennu are the most pristine space rocks scientists have ever held.

At the Lunar and Planetary Science Conference in Texas, scientists said that the sample contains a surprising reservoir of a mineral called magnesium phosphate. These bright-white particles sprinkled in a sea of Bennu's dark rocks is a rare find in astromaterials, they say.

In addition, they show the widespread presence of glycine, the simplest amino acid and a crucial ingredient of proteins, as well as other water-bearing minerals, including carbonates, sulfites, olivine and magnetite, all of which are tangible evidence that Bennu's parent body witnessed multiple water-related episodes before its fragments coalesced into Bennu.

Scientists also found abundant water-altered compounds called phyllosilicates, as well as a rich collection of other organic and hydrated minerals. Phyllosilicates, which are structurally bound to water in meteorites, may have been the cradles for organics and water that scientists suspect were delivered to Earth early in its history.

So, nothing Earth shattering yet. "We're still in the very early days of this very meticulous work," said Tim McCoy, a curator of meteorites at the Smithsonian's National Museum of Natural History in Washington, D.C. "There's a lot we don't know."


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