Surprising phosphate find in NASA OSIRIS-REx asteroid sample

Scientists have been eagerly awaiting the opportunity to dig into a pristine 4.3-ounce (121.6-gram) sample of asteroid Bennu collected by NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security—Regolith Explorer) mission since it was delivered to Earth. last fall They hoped the material would hold secrets to the solar system’s past and the prebiotic chemistry that may have led to the emergence of life on Earth.

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

The team analyzing the OSIRIS-REx samples found that Bennu contains the original components that formed our solar system. Asteroid 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 contains magnesium sodium phosphate, which was a surprise to the research team because it was not seen in the remote sensing data collected by the Benn spacecraft. Its presence in the sample suggests that the asteroid may have separated from a long-extinct, tiny, primitive ocean world.

Phosphate surprise

Analysis of the Bennu sample revealed interesting insights into the composition of the asteroid. The pattern, which is dominated by clay minerals, especially serpentine, reflects the type of rock found in mid-ocean ridges on Earth, where material from the mantle, the layer below the Earth’s crust, meets water.

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

While a similar phosphate was found in a sample of asteroid Ryugu delivered by JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 mission in 2020, the sodium magnesium phosphate detected in the Bennu sample stands out for its purity—that is, the lack of other materials in the sample. mineral—and its grain size, unprecedented in any meteorite sample.

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

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

“OSIRIS-REx gave us exactly what we were hoping for: a large, pristine sample of a nitrogen- and carbon-rich asteroid from a formerly wet world,” said Jason Dworkin, paper co-author and OSIRIS-REx project scientist at NASA’s Goddard Space. Flight center in Greenbelt, Maryland.

From a young solar system

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

“The sample we returned is the largest reservoir of unaltered asteroid material on Earth right now,” Lauretta said.

This composition offers a glimpse into the origins of our solar system more than 4.5 billion years ago. These rocks have preserved their original state, they have neither melted nor re-solidified since their formation, which confirms their ancient origin.

Tips on the building blocks of life

The team confirmed that the asteroid is rich in carbon and nitrogen. These elements are key to understanding the environment where Bennu’s materials formed and the chemical processes that transformed simple elements into complex molecules that potentially lay the foundations for life on Earth.

“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 the origin of life on Earth.”

What will be next

Dozens of other laboratories in the United States and around the world will receive portions of the Bennu sample from NASA’s Johnson Space Center in Houston in the coming months, and many more scientific papers describing Bennu sample analyzes are expected in the next few years. OSIRIS-REx Sample Analysis Team.

“The Bennu samples are tantalizingly beautiful alien rocks,” said Harold Connolly, co-author of the paper and OSIRIS-REx mission scientist at Rowan University in Glassboro, New Jersey. “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.”

The OSIRIS-REx probe, which was launched on September 8, 2016, traveled to the near-Earth asteroid Bennu and collected a sample of rocks and dust from the surface. OSIRIS-REx, the first US mission to collect a sample from an asteroid, delivered the sample to Earth on September 24, 2023.