Exciting Findings from Bennu Asteroid Sample
Researchers discovered traces of carbon, nitrogen, organic compounds, and… magnesium sodium phosphate. This unexpected mineral hints at a potentially water-rich past of Bennu.
On September 24, 2023, the OSIRIS-REx space probe returned to Earth after a visit to the asteroid Bennu. During this mission, the probe collected dust and debris, which were delivered to Earth on that memorable day. Since then, scientists have been extensively studying the samples. Now, they share their first notable discoveries.
Key Findings
Scientists have eagerly awaited the opportunity to examine the pristine 121.6 grams of Bennu sample, brought to Earth by NASA’s OSIRIS-REx mission last autumn. They hoped the material would reveal secrets about the past of our solar system and the prebiotic chemistry that might have contributed to the origin of life on Earth. Early analysis of the Bennu sample reveals exactly that.
The analysis of the Bennu sample has provided very interesting insights into the composition of the asteroid. The sample contains carbon, nitrogen, and organic compounds – all essential components for life as we know it. These elements are crucial for understanding the environments in which Bennu’s materials were formed and the chemical processes that transformed simple elements into complex molecules, potentially laying the groundwork for life on Earth. “These discoveries highlight the importance of collecting and studying material from asteroids like Bennu,” underscores Dante Lauretta, co-author and principal investigator for OSIRIS-REx. “Especially lightweight material, which would normally burn up upon entering the Earth’s atmosphere, offers valuable insights. This material is essential for understanding the complex processes that led to the formation of our solar system and the chemical steps that may have contributed to the origin of life on Earth.”
Mineral Composition
Additionally, the sample consists mainly of clay minerals, especially serpentine, and is reminiscent of the type of rock found at mid-ocean ridges on Earth, where material from the mantle, the layer beneath the Earth’s crust, comes into contact with water. This interaction leads not only to clay formation but also to various minerals such as carbonates, iron oxides, and iron sulfides.
Magnesium Sodium Phosphate Discovery
But the greatest surprise was the discovery that the sample contains water-soluble phosphates, particularly magnesium sodium phosphate. This mineral was a surprise because the OSIRIS-REx spacecraft hadn’t detected it during its stay at Bennu. Water-soluble phosphates are essential for the biochemistry of all known life forms on Earth. Although a similar phosphate was found in the Ryugu sample returned by JAXA’s Hayabusa2 mission in 2020, the magnesium sodium phosphate in the Bennu sample stands out for its exceptional purity—meaning the absence of other materials in the mineral—and the unprecedented large grain size, something never before observed in a meteorite sample.
Implications of the Discovery
The discovery of magnesium sodium phosphates in the Bennu sample raises questions about how these elements were concentrated by geochemical processes. This provides important clues about the conditions that existed on Bennu in the past. The presence of magnesium sodium phosphate in the Bennu sample suggests that the asteroid might originate from an ancient, small, primitive world with oceans. “The presence of phosphates, along with other elements and compounds on Bennu, indicates that the asteroid must have had a water-rich past,” suggests Lauretta. “It’s possible that Bennu was once part of a wetter world, although this hypothesis requires further research.”
Insights into the Early Solar System
Despite possible interactions with water in the past, Bennu remains a chemically primitive asteroid, with elemental ratios closely matching those of the sun. “We now possess the largest collection of unaltered asteroid material on Earth,” states Lauretta. This composition gives us a glimpse into the early days of our solar system, more than 4.5 billion years ago. These rocks have not melted or recrystallized since their formation, confirming that they have retained their original state and are thus very ancient.
Future Research
This initial analysis is just the tip of the iceberg. In the coming months, dozens of other laboratories will receive pieces of the Bennu sample, likely leading to numerous scientific articles detailing analyses of the Bennu sample in the years to come. “The Bennu samples are tantalizingly beautiful pieces of extraterrestrial rock,” says Harold Connolly, co-author and scientist for the OSIRIS-REx mission. “Every week, the OSIRIS-REx Sample Analysis Team brings forth new and sometimes surprising discoveries, providing crucial insights into the origin and evolution of planets like Earth.”
But we are not there yet. The current study, published in the journal Meteoritics & Planetary Science, is already a fantastic first step in understanding the Bennu samples. The analysis has not only increased our knowledge of asteroids but has also provided valuable insights into the building blocks of life and the dynamic processes that influenced the formation of our solar system. “OSIRIS-REx has delivered exactly what we hoped for: a large, pristine sample from an asteroid, rich in nitrogen and carbon from a bygone water-rich world,” concludes OSIRIS-REx project scientist Jason Dworkin.
