Recent research by faculty from Stony Brook University’s Department of Geosciences analyzed carbonaceous asteroid samples from Bennu, an asteroid visited by NASA’s OSIRIS-REx mission. It revealed the chemical composition of primitive solar system materials that are not possible to study, analyze or observe through remote sensing or conventional laboratory methods.
This research — “Nanoscale infrared spectroscopy reveals complex organic-mineral assemblages in asteroid Bennu,” by Research Associate Professor Mehmet Yesiltas, Professor and Department Chair Timothy Glotch, and Research Professor Paul Northrup — will be published in PNAS and was conducted in collaboration with researchers Andrew Dopilka and Robert Kostecki from Lawrence Berkeley National Laboratory.
The study is based on samples returned from the carbonaceous asteroid Bennu by NASA’s OSIRIS-REx mission, which is the second sample return mission from a carbonaceous asteroid, and the first one for the United States. Bennu is classified as a “primitive carbonaceous asteroid,” and is considered one of the best-preserved remnants of the early solar system, thus making its returned samples among the most scientifically valuable planetary materials currently available for study. Meteorites are traditionally considered a source of primitive asteroid materials; however, they carry the risk of being compromised by Earth’s atmospheric entry and terrestrial contamination. Bennu’s returned samples are considered genuinely pristine, making findings derived from them significantly more reliable.
This research group was one of the first teams selected to receive pieces of the returned asteroid samples for study. Using nanoscale-infrared and Raman spectroscopy, the group characterized the sample’s chemical composition at spatial resolutions down to ~20-500 nanometers/pixel. All measurements were performed without exposing the sample to air, as contact with the atmosphere can alter sensitive chemical bonds and organic functional groups, compromising the very signatures the researchers looked to detect. In addition, both techniques are non-destructive, which is an essential consideration given that these samples are irreplaceable.
At nanoscales, the fundamental building blocks of asteroid mineralogy and organic chemistry can be directly observed in such pristine and precious samples. The group’s analysis identified distinct chemical domains, such as aliphatic-rich, carbonate-rich and nitrogen-bearing organic-rich regions. This demonstrates that water-driven alteration on Bennu was chemically heterogeneous. The nitrogen-bearing organic functional groups are widely preserved despite extensive aqueous alteration.
“These findings carry broader significance for planetary science and astrobiology,” said Yesiltas. “They demonstrate survival of chemically labile, nitrogen-bearing organics through aqueous alteration on a small solar system body has direct implications for long-standing questions about how organic complexity is built up and preserved in primitive planetary materials. By extension, it may reveal how organics relevant to prebiotic chemistry may have been delivered to early Earth via carbonaceous asteroids and may have played a role in the chemical processes that might have eventually led to life.”
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