Bennu asteroid analysis suggests unexpected origins for organics in space

Samples from the asteroid Bennu and the Murchison meteorite contain molecules that build proteins necessary for life, according to recent research. Phys.org reported that a team including researchers at Penn State studied these amino acids using a new technique to look at isotopes, which are slight variations in the mass of molecular compounds' atoms. The Bennu sample was delivered in 2023 by NASA's OSIRIS-REx mission, providing material direct from space without terrestrial contamination, while the Murchison meteorite fell to Earth in 1969. The research findings were published in Nature Communications Earth & Environment. According to the researchers, the wide range of isotope values measured within the amino acids suggest that carbon and nitrogen atoms within the molecules originated in different parts of the solar system. Ophélie Mcintosh, former postdoctoral researcher in Penn State's Department of Geosciences and lead author on the paper, stated that amino acids provide a direct link between space chemistry and the origins of life on Earth. Most studies focus on the distribution and quantification of amino acids, but the team's question about how they are formed is quite new, utilizing unique isotope instruments including one that exists only at Penn State. Christopher House, professor of geosciences and co-author on the paper, noted that isotope ratios provide a measurable tag linking molecules to specific reservoirs or processes. The team previously examined glycine, finding it may have formed in a harsh, cold environment rather than under warm and wet conditions. In the new study, they focused on beta-alanine, one of the most abundant amino acids found in asteroid and meteorite samples. Katherine Freeman, Evan Pugh University Professor and principal investigator on the project, explained that beta-alanine helps researchers understand why there are many different types of these compounds and where and how they were made. Traditional isotopic analyses take an average of the carbon isotopes in a molecule, but the Penn State researchers developed a new technique to look at individual carbon isotopes within the molecule. This intramolecular information provides a detailed isotopic fingerprint to distinguish between possible formation pathways. Two pieces of equipment enabled these measurements: the pico-CSIA at Penn State, which measures isotopic averages of extremely small amounts of material, and a modified GC-Orbitrap that measures isotope compositions at different positions within the molecule. When comparing the Bennu and Murchison samples, the carbon isotope average was nearly the same within the margin of error, but the intramolecular carbon measurements were completely different. The enriched Bennu carbon measured as the highest ever recorded isotope anomaly in an organic molecule from space. Freeman expressed being gobsmacked by the enormous isotope difference between neighboring atom positions within the same molecule, indicating the primordial nature of these molecules formed at the dawn of the solar system. While the isotope values varied, the isotopic structure was similar, suggesting the two samples may share a related underlying chemistry and formation process while originating in different parts of the solar system. Although the OSIRIS-REx mission has concluded, Freeman stated that an important next step is to study how space environments and processes, such as exposure to water, impact the order of isotopes within molecules.