Scientists studying samples from the asteroid Bennu have uncovered a surprisingly complex chemical landscape at the tiniest scales.
A new study shows that, at an extremely small scale, organic material and minerals inside the asteroid Bennu are organized into three clearly different chemical groupings. These patterns provide important clues about how liquid water once altered the asteroid.
Bennu is a carbon-rich asteroid located relatively close to Earth. It formed from fragments left behind after its original parent body broke apart. Because the samples returned from Bennu have not been exposed to Earth’s atmosphere or weather, they offer a rare, untouched record of how water, minerals, and organic compounds interacted in the early Solar System.
Nanoscale Analysis of OSIRIS-REx Sample
Mehmet Yesiltas and his team examined a sample known as OREX-800066-3, collected during NASA’s OSIRIS-REx mission and delivered to Earth in September 2023. To study the material in detail, the researchers used nanoscale infrared spectroscopy along with Raman spectroscopy, allowing them to analyze chemical variations at scales of about 20 nanometers.
Their results show that the distribution of organic matter and minerals is uneven. Instead of being mixed uniformly, the material forms three recurring types of organic–mineral regions. One region is dominated by aliphatic organic compounds, another contains abundant carbonate minerals, and a third is rich in nitrogen-containing organic compounds.
Evidence of Water Shaping Bennu’s Chemistry
This uneven, nanoscale structure indicates that water did not affect Bennu in a single, uniform way. Instead, water interacted differently in separate areas, producing a patchwork of chemical environments across the asteroid.
The study also found that delicate organic molecules were able to survive these water-related processes. According to the authors, these findings provide deeper insight into how water, minerals, and organic matter interacted on primitive asteroids, helping scientists better understand the early conditions that shaped the Solar System.
Reference: “Nanoscale infrared spectroscopy reveals complex organic–mineral assemblages in asteroid Bennu” by Mehmet Yesiltas, Andrew Dopilka, Robert Kostecki, Timothy D. Glotch and Paul Northrup, 30 March 2026, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2601891123
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