Surprising phosphate finds in NASA’s OSIRIS-REx asteroid sample

Scientists have been eagerly awaiting the opportunity to dig into the pristine sample of the 121.6-gram asteroid Bennu collected by NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer) mission since it launched on earth was delivered. last fall. They hoped the material would hold secrets about the solar system’s past and the prebiotic chemistry that might have led to the origins of life on Earth.

An early analysis of the Bennu sample, published in Meteoritics and planetary scienceshows that this excitement was justified.

The OSIRIS-REx Sample Analysis Team discovered that Bennu contains the original ingredients that formed our solar system. The asteroid’s dust is rich in carbon and nitrogen, as well as organic compounds, all of which are essential components of life as we know it. The sample also contained magnesium sodium phosphate, which was a surprise to the research team as it was not seen in the remote sensing data collected by the spacecraft on Bennu. Its presence in the sample suggests that the asteroid could have split off from a long-vanished, small, primitive ocean world.

A phosphate surprise

Analysis of the Bennu sample provided intriguing insights into the asteroid’s composition. The sample is dominated by clay minerals, particularly serpentine, and reflects the type of rock found at mid-ocean ridges on Earth, where material from the mantle, the layer beneath the Earth’s crust, encounters water.

This interaction not only results in the formation of clays; it also gives rise to a variety of minerals such as carbonates, iron oxides and iron sulfides. But the most unexpected discovery is the presence of water-soluble phosphates. These compounds are components of the biochemistry of all life on Earth today.

Although a similar phosphate was found in the asteroid Ryugu sample delivered in 2020 by JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 mission, the magnesium-sodium phosphate detected in the Bennu sample is notable for its purity – which i.e. due to the absence of other materials in the sample. the mineral – and the size of the grains, unprecedented in any meteorite sample.

The discovery of magnesium-sodium phosphates in the Bennu sample raises questions about the geochemical processes that concentrated these elements and provides valuable clues about Bennu’s historical conditions.

“The presence and state of phosphates, along with other elements and compounds on Bennu, indicate a watery past for the asteroid,” said Dante Lauretta, co-lead author of the paper and principal investigator of OSIRIS-REx at the University of Arizona. Tucson. “Bennu could possibly have once been part of a wetter world, although this hypothesis requires further research.”

“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 Jason Dworkin, co-author of the paper and OSIRIS-REx project scientist at NASA’s Goddard Space. Flight Center in Greenbelt, Maryland.

From a young solar system

Despite its possible history of interacting with water, Bennu remains a chemically primitive asteroid, with elemental proportions very similar to those of the Sun.

“The sample we returned is currently the largest reservoir of unaltered asteroid material on Earth,” Lauretta says.

This composition offers a glimpse into the early days of our solar system, more than 4.5 billion years ago. These rocks have retained their original state and have not melted or re-solidified since their creation, confirming their ancient origins.

Tips for the building blocks of life

The team confirmed that the asteroid is rich in carbon and nitrogen. These elements are crucial for understanding the environments from which Bennu’s materials came and the chemical processes that transformed simple elements into complex molecules, potentially laying the foundation for life on Earth.

“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.”

What’s next

Dozens of laboratories in the United States and around the world will receive parts of the Bennu sample from NASA’s Johnson Space Center in Houston in the coming months, and many more scientific papers are expected in the coming years that will further analyze the Bennu sample to describe. OSIRIS-REx sample analysis team.

“The Bennu samples are tantalizingly beautiful alien rocks,” said Harold Connolly, co-lead author of the paper and OSIRIS-REx mission sample scientist at Rowan University in Glassboro, New Jersey. “Each week, analysis by the OSIRIS-REx Sample Analysis Team produces new and sometimes surprising findings that help place important constraints on the origin and evolution of Earth-like planets.”

The OSIRIS-REx spacecraft, launched on September 8, 2016, traveled to the near-Earth asteroid Bennu and collected a sample of rocks and dust from its surface. OSIRIS-REx, the first U.S. mission to collect a sample from an asteroid, returned the sample to Earth on September 24, 2023.