Asteroid Bennu has surprisingly watery past, researchers say | CNN

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Early analysis of a sample taken from the asteroid Bennu suggests the space rock may have had an unexpectedly watery past, possibly even splitting off from an ancient ocean planet.

NASA’s OSIRIS-REx mission scooped up 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 delivered the elements for life on Earth. Asteroids also intrigue scientists because they are the leftovers from the formation of the solar system.

An initial examination of part of the sample, shared in October, suggested the asteroid contained a large amount of carbon.

In 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 know it and could 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 hoped for: a large, pristine asteroid sample, rich in nitrogen and carbon, from a previously 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 initially not 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 serves as a lifelong part of biochemistry.

It is possible that the asteroid broke off from a small, primitive ocean world that no longer exists in our solar system, the researchers said.

The asteroid sample is largely composed of clay minerals, including serpentine, making it remarkably similar to rocks found on Earth at mid-ocean ridges. These ridges are where material from the mantle, the layer beneath the Earth’s crust, encounters 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 status of phosphates, along with other elements and compounds on Bennu, suggest a watery past for the asteroid,” said co-lead study author Dante Lauretta, principal investigator for OSIRIS-REx and a 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 investigation.”

The rocks collected at Bennu represent a time capsule from the early days of the solar system that is more than 4.5 billion years old.

“The sample we returned is the largest reservoir of unaltered asteroid material on Earth today,” 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 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 – especially low-density material that would normally burn up as it enters Earth’s atmosphere,” Lauretta said. “This material holds the key to unraveling the complicated processes of solar system formation and the prebiotic chemistry that could have contributed to the origins of life on Earth.”

The wealth of material collected from the asteroid means that more labs around the world will receive their own pieces of the sample to study.

“The Bennu samples are tantalizingly beautiful alien rocks,” said study co-lead author Harold Connolly Jr., OSIRIS-REx mission sample scientist and chair of the department of geology at Rowan University’s School of Earth & Envrionment in Glassboro, New Jersey, in a statement. “Each week, analysis by the OSIRIS-REx Sample Analysis Team yields new and sometimes surprising findings that help place important constraints on the origin and evolution of Earth-like planets.”