HOUSTON – New analysis of samples collected from asteroid Bennu reveals a surprisingly active surface and a composition rich in water-bearing minerals, according to research published this week in Nature Geoscience. The findings suggest Bennu is undergoing rapid weathering and has a complex history involving both icy accretion and internal heating.
Researchers steadfast that approximately 80 percent of Bennu’s sample consists of minerals containing water. “We suspect that the parent asteroid collects a lot of ice material from the outside solar system and then … a little hot (appearing) to melt the ice and cause the fluid to react with solids,” explained Dr. Zega, a researcher involved in the OSIRIS-REx mission.
the OSIRIS-REx mission, launched by NASA in 2016, successfully collected a sample from bennu in october 2020 and returned it to Earth in September 2023. The sample’s analysis is ongoing at NASA’s Johnson Space Center in Houston, Texas.
Further investigation of the Bennu sample revealed microscopic craters and evidence of melted rock. These features indicate that Bennu is continually bombarded by micrometeorites,contributing to its surface weathering. “Bennu surface weathering occurs much faster than expected,” stated Lindsay Keller from NASA Johnson Space Center. This weathering is driven by both impacts and exposure to solar radiation.
Bennu, classified as a potentially hazardous asteroid due to its orbit crossing Earth’s, measures approximately 500 meters (1,640 feet) in diameter. Scientists believe Bennu is a fragment of a larger asteroid that formed in the early solar system,approximately 4.5 billion years ago. The asteroid’s composition provides valuable insights into the building blocks of our solar system and the delivery of water and organic molecules to early Earth.
The research team’s findings build upon previous analyses of Bennu’s surface conducted during the OSIRIS-REx mission’s orbital phase. These observations already indicated the presence of hydrated minerals and a surprisingly dark surface, prompting further investigation upon sample return.
The ongoing analysis of the Bennu sample is expected to yield further discoveries about the asteroid’s formation, evolution, and potential role in the origins of life. The samples are being carefully preserved and studied by an international team of scientists.
