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An early analysis of a sample collected from the asteroid Bennu suggests the space rock may have had an unexpected watery past. The rock may even have split off from an ancient ocean planet.
NASA’s OSIRIS-REx mission collected the 121.6-gram pristine sample of the Earthgrazer 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 assessment of part of the sample, shared in October, suggested the asteroid contained a large amount of carbon.
During reanalysis of the sample, the team found that Bennu’s dust is rich in carbon, nitrogen and organic compounds, all of which contributed to the formation of the solar system. These ingredients are also essential to life as we know it and can help scientists better understand how planets like Earth evolve.
A study detailing the findings was published Wednesday in the journal Meteoritics & Planetary Science.
“OSIRIS-REx gave us exactly what we were hoping for: a large, pristine asteroid sample, rich in nitrogen and carbon, 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 a statement.
The biggest surprise was the discovery of magnesium sodium phosphate in the sample, which was not initially detected using remote sensing when OSIRIS-REx, or the Origins, Spectral Interpretation, Resource Identification, and Security — Regolith Explorer mission, orbited Bennu.
Magnesium sodium phosphate is a compound that can be dissolved in water and is part of the biochemistry of life.
It is possible that the asteroid broke off a tiny, primitive ocean world that no longer exists in our solar system, the researchers say.
The asteroid sample is composed largely of clay minerals, including serpentine, making the sample remarkably similar to rocks found at mid-ocean ridges on Earth. These ridges are the places where material from the mantle, the layer beneath the Earth’s crust, comes into contact with water.
A similar phosphate was found in a sample of the asteroid Ryugu 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 state of phosphates, along with other elements and compounds on Bennu, suggest a watery past for the asteroid,” said study co-lead author Dante Lauretta, principal investigator for OSIRIS-REx and regents professor at the University of Arizona, Tucson, in a statement. “Bennu could once have been part of a wetter world. Although, this hypothesis requires further research.”
The rocks collected on Bennu form 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 today,” Lauretta said.
Astronomers think that space rocks such as asteroids and comets may have served as messengers in our solar system.
“This means that asteroids like this may have played a key role in providing water and the building blocks of life on Earth,” said co-author Nick Timms, member of the OSIRIS-REx Sample Analysis team and associate professor at the Curtin University’s School of Earth and Planetary. Sciences, in a statement.
If these smaller rocky bodies carried water, minerals and other elements and crashed into Earth as it formed billions of years ago, they could have laid the foundation for the emergence of life on our planet.
“These findings underscore the importance of collecting and studying material from asteroids like Bennu — particularly low-density material that normally burns up as it enters Earth’s atmosphere,” Lauretta said. “This material is key to unraveling the intricate processes that formed the solar system and the prebiotic chemistry that may have helped give rise to life on Earth.”
The wealth of material collected from the asteroid means more labs around the world will receive their own pieces of the sample to study.
“The Bennu samples are tantalizingly beautiful alien rocks,” study co-lead author Harold Connolly Jr., OSIRIS-REx mission sample scientist and head of the geology department at Rowan University’s School of Earth & Environment in Glassboro, New Jersey, said in a statement. “Every week, analysis by the OSIRIS-REx Sample Analysis Team produces new and sometimes surprising findings that help provide important constraints on the origin and evolution of Earth-like planets.”