An initial analysis of a sample collected from the asteroid Bennu suggests the space rock had an unexpectedly water-rich past — and may even have broken off from an ancient ocean world.
NASA’s (United States space agency) OSIRIS-REx mission collected the pristine 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 hold about the asteroid’s composition and whether it could have provided the elements for life on Earth. Asteroids also intrigue scientists because they are the remnants of the formation of the Solar System.
An initial review of part of the sample, shared in October, suggested that the asteroid contained a large amount of carbon.
During a new analysis of the sample, the team discovered 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 to life as we understand it and can help scientists better understand how Earth-like planets evolve.
A study detailing the findings was published on Wednesday (26) in Meteoritics & Planetary Science magazine.
“OSIRIS-REx gave us exactly what we expected: a large, pristine, nitrogen- and carbon-rich asteroid sample from a formerly wet world,” said Jason Dworkin, study co-author and OSIRIS-REx project scientist at NASA’s Goddard Space Flight Center. NASA in Greenbelt, Maryland, in a statement.
Elements for life
The biggest surprise was finding magnesium-sodium phosphate within the sample, which remote sensing initially failed to detect when OSIRIS-REx, or the Origins, Spectral Interpretation, Resource Identification, and Security — Regolith Explorer mission, was orbiting Bennu.
Magnesium-sodium phosphate is a compound that can be dissolved in water and serves as a component of the biochemistry of life.
It’s possible the asteroid may have broken off from a small, primitive oceanic world that no longer exists in our Solar System, researchers said.
The asteroid sample consists mainly 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 beneath Earth’s surface crust, meets water.
A similar phosphate was found in a sample of asteroid Ryugu collected by the Japan Aerospace Exploration Agency’s Hayabusa2 mission and returned to Earth in December 2020. But the compound in the Bennu sample is purer and has larger grains.
“The presence and state of phosphates, along with other elements and compounds on Bennu, suggest an aqueous past for the asteroid,” said Dante Lauretta, study co-author, OSIRIS-REx principal investigator and Regents Professor at the University of Arizona in Tucson (USA), in a statement. “Bennu potentially could have been part of a wetter world. However, this hypothesis requires further investigation.”
Cosmic time capsules
The rocks collected from Bennu represent a time capsule of the early days of the Solar System, dating back more than 4.5 billion years.
“The sample we brought back is the largest reservoir of undisturbed 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 one may have played a key role in delivering water and the building blocks of life to Earth,” said study co-author Nick Timms, member of the OSIRIS-REx Sample Analysis team and professor associate in the School of Earth and Planetary Sciences at Curtin University (USA), in a statement.
If these small rocky bodies were carrying water, minerals and other elements and collided with 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 highlight the importance of collecting and studying material from asteroids like Bennu — especially low-density material that would normally burn up upon entering Earth’s atmosphere,” Lauretta said. “This material holds the key to unlocking the intricate processes of the formation of the Solar System and the prebiotic chemistry that could have contributed to the emergence of life on Earth.”
The abundance of material collected from the asteroid means that more laboratories around the world will receive their own parts of the sample for study.
“The Bennu samples are wonderfully intriguing extraterrestrial rocks,” said Harold Connolly Jr., study co-author, sample scientist for the OSIRIS-REx mission and head of the geology department at the School of Earth and Environment at Rowan University in Glassboro. New Jersey in a statement. “Each week, analysis by the OSIRIS-REx Sample Analysis team provides new and sometimes surprising discoveries that are helping to establish important constraints on the origin and evolution of Earth-like planets.”
NASA mission reveals details about asteroid that could collide with Earth
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