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An early analysis of a sample collected from asteroid Bennu suggests the space rock had an unexpectedly water-rich past — and may even have broken off from an ancient oceanic world.
NASA’s OSIRIS-REx mission retrieved the pristine 4.3 ounce (121.6 gram) sample from the near-Earth asteroid in 2020 and returned it to Earth last September.
Since then, scientists have been analyzing the asteroid’s rocks and dust to see what secrets they might contain about the asteroid’s composition and whether it could have delivered the elements for life on Earth. Asteroids also intrigue scientists because they are leftovers from the formation of the solar system.
An initial review of some of the samples, shared in October, suggested the asteroid contained a large amount of carbon.
During a new analysis of the sample, the team found that Bennu’s dust is rich in carbon, nitrogen and organic compounds, all of which helped form the solar system. These ingredients are also essential for life as we understand it and can help scientists better understand how Earth-like planets evolve.
A study detailing the findings appeared Wednesday in the journal Meteoritics & Planetary Science.
“OSIRIS-REx gave us exactly what we hoped for: a large sample of pristine, nitrogen- and carbon-rich asteroids from a once-wet world,” said study co-author Jason Dworkin, OSIRIS-REx project scientist at the Flight Center. NASA’s Goddard Space Facility in Greenbelt, Maryland. in a statement.
The biggest surprise was finding magnesium-sodium phosphate within the sample, which the remote sensor didn’t initially detect when OSIRIS-REx, or the Origins, Spectral Interpretation, Source Identification and Security – Regolith Explorer mission, was orbiting Bennu.
Magnesium-sodium phosphate is a water-soluble compound that serves as a component of biochemistry for life.
It is possible that the asteroid may have broken away from a small primitive oceanic world that no longer exists in our solar system, researchers said.
The asteroid sample is composed mostly of clay minerals, including serpentine, which makes the sample remarkably similar to rocks found at mid-ocean ridges on Earth. These ridges are where material from the mantle, the layer below the Earth’s surface crust, meets water.
A similar phosphate was found in a sample from the Ryugu asteroid collected by the Japan Aerospace Exploration Agency’s Hayabusa2 mission and returned to Earth in December 2020. But the compound from the Bennu sample is purer and has larger grains.
“The presence and condition of phosphates, along with other elements and compounds in Bennu, suggest an aqueous past for the asteroid,” said study author Dante Lauretta, principal investigator for OSIRIS-REx and regents professor at the University of Arizona. Tucson, in a statement. “Bennu could potentially have once been part of a wetter world. However, this hypothesis requires further investigation.”
The rocks collected from Bennu represent a time capsule from the early days of the solar system dating back more than 4.5 billion years.
“The sample we returned is the largest reservoir of unchanged asteroid material on Earth right now,” Lauretta said.
Astronomers believe that space rocks such as asteroids and comets may have served as ancient messengers to our solar system.
“This means that asteroids like this may have played a key role in the distribution of water and the building blocks of life on Earth,” said study co-author Nick Timms, a member of the OSIRIS-REx sample analysis team and professor of associate at Curtin University’s School of Earth and Planetary Sciences. Science, in a statement.
If these smaller rocky bodies had carried water, minerals and other elements and crashed into Earth as it was forming billions of years ago, they could have helped set the stage for the beginning of life on our planet.
“These findings underscore the importance of collecting and studying material from asteroids like Bennu — especially the low-density material that would normally burn up upon entering Earth’s atmosphere,” Lauretta said. “This material holds the key to unraveling the complex processes of solar system formation and the prebiotic chemistry that may have contributed to the emergence of life on Earth.”
The wealth of material collected from the asteroid means that more laboratories around the world will receive their own sample pieces to study.
“The Bennu samples are extremely beautiful extraterrestrial rocks,” said study author Harold Connolly Jr., sample scientist for the OSIRIS-REx mission and chair of the geology department at Rowan University’s School of Earth and Environment in Glassboro, New Jersey. in a statement. “Each week, analysis by the OSIRIS-REx Sample Analysis Team provides new and sometimes surprising findings that are helping to place important constraints on the origin and evolution of Earth-like planets.”