Adapted from this ALS Science Highlight
In 2023, NASA returned material gathered from the 4.5-billion-year-old asteroid Bennu, which formed from minerals and ice in a primordial nebula. The rocks were gathered as part of NASA’s OSIRIS-REx mission, the first US mission to return samples from an asteroid. Lawrence Berkeley National Laboratory (Berkeley Lab) continues to participate in a series of multi-institutional research studies investigating Bennu’s chemical makeup to better understand how our solar system and planets evolved.
Past research on Bennu samples at Berkeley Lab’s ALS revealed that many minerals formed in watery environments. In the current study, the researchers rolled back the clock to examine a narrow period shortly after the asteroid formed but before it was exposed to the water that altered the chemical nature of the rock.
The researchers identified long chains of organic molecules, richer in nitrogen and oxygen than the previous samples. With this information, the team reconstructed the conditions during the earliest periods of the asteroid’s existence. Their work was recently published in Nature Astronomy.
A large number of researchers from many institutions have used a wide variety of techniques to study samples from Bennu. For this analysis, a team of researchers worked together including scientists from the NASA Ames Research Center (ARC), University of California, Berkeley’s Space Sciences Laboratory, Washington University, California State University San Marcos, NASA Goddard Space Flight Center (GSFC), University of Arizona, Berkeley Lab’s Molecular Foundry and Advanced Light Source, and more. The multidisciplinary and multi-facility collaboration yielded a robust characterization of Bennu.
At the Foundry, the samples were carved into thin, microscopic sections. The team used transmission electron microscopy to obtain sharp images of the specimen and determine the crystallinity of the constituents.
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By comparing data from the Foundry and the Advanced Light Source, the team confirmed the material’s unique organic composition. Based on the substance’s chemical nature, they reconstructed the environment that would support its formation.
The team suggested the organic compounds formed when heat from the radioactive decay of unstable atoms in the rock warmed the asteroid. The frozen chunks of ammonia and carbon dioxide combined chemically to form carbamates, which subsequently polymerized into a gum-like material. The nitrogen-rich composition of carbamate may have played a role in the formation of amino acids, nucleobases, and other chemical precursors that could have contributed to the prebiotic inventory necessary for the emergence of life.
Read more about these Bennu findings in the NASA press release.
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