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Early analysis of a sample taken from the asteroid Bennu suggests the space rock had an unexpectedly rich past — and may have even separated from an ancient ocean world.
NASA’s OSIRIS-REx mission collected a 4.3-ounce (121.6-gram) pristine sample from a 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 hold about the asteroid’s composition and whether it could have supplied the elements for life on Earth. Asteroids also attract scientists because they are leftovers from the formation of the solar system.
An initial inspection of some of the samples, shared in October, indicated that the asteroid contained large amounts 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 components are also essential for life as we understand it, and could help scientists better understand how Earth-like planets evolve.
A study detailing the findings appeared Wednesday in the journal Meteoritics & Planetary Science.
“OSIRIS-REx provided us with exactly what we were hoping for: a large, pristine sample of a nitrogen- and carbon-rich asteroid from a formerly wet world,” said study co-author Jason Dworkin, OSIRIS-REx project scientist at NASA’s Goddard Space Flight Center in Greenbelt. Maryland. in the statement.
The biggest surprise was the discovery of sodium magnesium phosphate in the sample, which was not initially detected by remote sensing when OSIRIS-REx, or the Origins, Spectral Interpretation, Resource Identification and Security — Regolith Explorer mission, orbited Benna.
Sodium magnesium phosphate is a compound that can be dissolved in water and serves as part of the biochemistry for life.
Lauretta & Connolly et al. (2024)/Meteoritics and Planetary Science
A microscopic image shows a dark particle from Bennu, about a millimeter long, with a light phosphate crust.
It is possible that the asteroid broke away a small, primitive ocean world that no longer exists in our solar system, scientists said.
The asteroid sample is largely composed of clay minerals, including serpentine, making 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 crust, meets water.
A similar phosphate was found in a sample from the Ryugu asteroid collected by the Japanese Space 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 state of phosphates, along with other elements and compounds, on Bennu suggests a watery past for the asteroid,” said study co-author Dante Lauretta, OSIRIS-REx principal investigator and Regents Professor at the University of Arizona. Tucson, in a statement. “Bennu may once have been part of a wetter world. However, this hypothesis requires further investigation.”
Rocks collected from Bennu represent a time capsule from the early days of the solar system, dating back more than 4.5 billion years.
Erika Blumenfeld/Joseph Aebersold/NASA
Rocks and dust were collected from the asteroid Bennu and returned to Earth by the OSIRIS-REx mission.
“The sample we returned is the largest reservoir of unaltered asteroid material on Earth right now,” Lauretta said.
Astronomers believe that space rocks such as asteroids and comets may have served as ancient messengers in our solar system.
“This means that asteroids like this could have played a key role in supplying 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 associate professor at Curtin University’s School of Earth and Planetary. Sciences, in statement.
If these smaller rocky bodies, carrying water, minerals and other elements, had hit Earth during its formation billions of years ago, they could have helped set the stage for 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 is key to unraveling the complex processes of solar system formation and the prebiotic chemistry that may have contributed to life emerging on Earth.”
The wealth of material collected from the asteroid means that more laboratories around the world will receive their own pieces of the sample to study.
“The Bennu samples are tantalizingly beautiful alien rocks,” study co-author Harold Connolly Jr., OSIRIS-REx sample scientist and chair of the geology department at Rowan University’s School of Earth & Envrionment in Glassboro, New Jersey, said in a statement. “Each week, analysis by the OSIRIS-REx sample analysis team provides new and sometimes surprising findings that help place important constraints on the origin and evolution of Earth-like planets.”