Scientists Find Presolar Stardust in Samples from Asteroid Bennu

Researchers have detected an unexpected abundance of presolar grains – dust from stellar explosions that predate our solar system – in samples from the near-Earth asteroid (101955) Bennu collected by NASA’s OSIRIS-Rex spacecraft.

Characterization of a presolar spinel-hibonite grain from the asteroid Bennu. Image credit: Nguyen and others., doi: 10.1038/s41550-025-02688-3.

“Presolar stardust grains are found in trace amounts in meteorites, interplanetary dust particles, Antarctic meteorites, samples from Comet 81 P/Wild2 returned by NASA’s Stardust mission, and samples from the carbonaceous asteroid Ryugu returned by JAXA’s Hayabusa-2 mission,” said Dr. Ann Nguyen of NASA’s Johnson Space Center and her colleagues. colleagues.

“Their highly anomalous isotopic compositions result from nucleosynthetic reactions in evolved red giant stars, supernovae, and novae.”

“The mineralogy and chemistry of presolar grains can be used to constrain condensation conditions and to probe the effects of secondary weathering, as these grains are susceptible to alteration or destruction in space, in the solar nebula, and within planetesimals.”

In the study, scientists analyzed presolar grains found in two different rock types in the Bennu samples.

The samples contained six times more grains than any other astromaterial studied, suggesting that the asteroid’s parent body formed in a region of the protoplanetary disk enriched with dust from dying stars.

The study also reveals that although Bennu’s parent asteroid has undergone significant fluid alteration, there are still pockets of less altered material in the samples that offer insight into its origin.

“These fragments retain a greater abundance of organic matter and presolar silicate grains, which are known to be easily destroyed by asteroidal aqueous weathering,” Dr. Nguyen said.

“Their preservation in the Bennu samples was a surprise and illustrates that some materials escaped alteration in the parent body.”

“Our study reveals the diversity of presolar materials that the parent has accumulated during its formation.”

An article on the results was published on December 2 in the journal Natural astronomy.

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AN Nguyen and others. Abundant supernova dust and heterogeneous aqueous alteration revealed by stardust in two lithologies of the asteroid Bennu. Nat Astronpublished online December 2, 2025; doi: 10.1038/s41550-025-02688-3