Tucson Standard

A deep dive into the sample of rocks and dust returned from near-Earth asteroid Bennu by NASA's University of Arizona-led OSIRIS-REx mission has revealed some long-awaited surprises.

Bennu contains the original ingredients that formed our solar system, the OSIRIS-REx Sample Analysis Team found. The asteroid's dust is rich in carbon and nitrogen, as well as organic compounds, all of which are essential components for life as we know it. The sample also contains magnesium sodium phosphate, which was a surprise to the research team because it wasn't seen in the remote sensing data collected by the spacecraft at Bennu. Its presence in the sample hints that the asteroid could have splintered off from a long-gone, tiny, primitive ocean world.

Launched on Sept. 8, 2016, the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer spacecraft, dubbed OSIRIS-REx, began its journey to near-Earth asteroid Bennu to collect a sample of rocks and dust from the surface. OSIRIS-REx was the first U.S. mission to collect a sample from an asteroid. The spacecraft delivered the sample, weighing 4.3 ounces or 121.6 grams, to Earth on Sept. 24, 2023.

"Finally having the opportunity to delve into the OSIRIS-REx sample from Bennu after all these years is incredibly exciting," said Dante Lauretta, principal investigator for OSIRIS-REx and Regents Professor of planetary sciences in the University of Arizona Lunar and Planetary Laboratory. "This breakthrough not only answers longstanding questions about the early solar system but also opens new avenues of inquiry into the formation of Earth as a habitable planet."

Lauretta is co-lead author of a paper published in Meteoritics & Planetary Science that details the nature of the asteroid sample. The paper also serves as an introduction to the Bennu sample catalog, an online resource where information about the sample is made publicly available and where scientists can request sample material for their own research.

"The publication of the first paper led by Dr. Lauretta and Dr. Connolly describing the Bennu sample is an exciting milepost for the mission and for the Lunar and Planetary Laboratory," said Mark Marley, director of UArizona Lunar and Planetary Laboratory and head of Department of Planetary Sciences. "Our faculty, scientists and students will continue to study this sample for years and decades to come."

Analysis of Bennu's composition unveiled intriguing insights into its makeup. Dominated by clay minerals like serpentine, it mirrors rock found at mid-ocean ridges on Earth where mantle material encounters water.

This interaction results in clay formation and gives rise to various minerals including carbonates, iron oxides, and iron sulfides. However, water-soluble phosphates were unexpectedly discovered in Bennu's samples.

A similar phosphate was found in Japan Aerospace Exploration Agency's Hayabusa2 mission's Ryugu samples in 2020 but magnesium sodium phosphate detected in Bennu stands out due to its lack of inclusions and grain size.

"The presence and state of phosphates suggest a watery past for Bennu," Lauretta said.

Despite possible water interaction history, Bennu remains chemically primitive with elemental proportions resembling those of our sun.

"The sample we returned is largest reservoir unaltered asteroid material on Earth right now," Lauretta said.

The team confirmed that Bennu is rich in carbon and nitrogen which are crucial for understanding environments from which its materials originated potentially laying groundwork for life on Earth.

"These findings underscore importance collecting studying material from asteroids like Bennu especially low-density material that would typically burn up upon entering Earth's atmosphere," Lauretta added.

Dozens more labs globally will receive portions from NASA’s Johnson Space Center Houston with many more scientific papers expected over next few years detailing findings by OSIRIS-REx Sample Analysis Team.

"The Bennu samples are tantalizingly beautiful extraterrestrial rocks," said Harold Connolly co-lead author professor Rowan University visiting research scientist UArizona "Each week analysis provides new sometimes surprising findings helping place important constraints origin evolution Earthlike planets."

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