This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Samples from the Bennu asteroid, which is currently more than 200 million miles (322 million kilometers) from Earth, and the Murchison meteorite, which fell to Earth in 1969, both contain molecules that build proteins necessary for life. New research has found that the molecules may have formed through the same process but originated far from one another in the solar system.
Using a new technique to look at isotopes, or slight variations in the mass of the molecular compounds' atoms, a team including researchers at Penn State studied the molecules, called amino acids, from a sample of Bennu, delivered in 2023 by NASA's OSIRIS-REx mission, and from a sample of Murchison. The Bennu sample, direct from space and without terrestrial contamination, gave insight into where these molecules might have formed. According to the researchers, who published their findings in Communications Earth & Environment, the wide range of isotope values measured within the amino acids in the Bennu asteroid and Murchison meteorite samples was surprising and suggests that carbon and nitrogen atoms within the molecules originated in different parts of the solar system.
"Amino acids are the building blocks of proteins and peptides, but they are also found in carbon-rich meteorites and asteroid samples, so they can provide a direct link between space chemistry and the origins of life on Earth," said Ophélie Mcintosh, a former postdoctoral researcher in Penn State's Department of Geosciences and lead author on the paper. "Most studies focus on the distribution and quantification of amino acids, so our question about how they're formed is quite new. We used unique isotope instruments, including one that exists only at Penn State, to help answer those questions." To understand how these molecules were formed, researchers measured the isotopes, finding clues to the chemicals the isotopes came from and how they ended up in the molecule under study.
"Isotope ratios provide a measurable tag that can link molecules to specific reservoirs or processes," said Christopher House, professor of geosciences and co-author on the paper. "For our study, isotopes provided clues to an older history for specific atoms in a molecule." The team previously looked at glycine, the simplest and most abundant amino acid, and found that the glycine on Bennu may have formed in a harsh, cold environment—which goes against the prevailing idea that the building blocks of life formed under warm and wet conditions. This time, they focused on the amino acid beta-alanine.
Beta-alanine is not one of the 20 amino acids that form proteins, but it is naturally produced in the human body and can combine with other amino acids to make peptides that can act as molecular enzymes. It is also one of the most abundant amino acids found in asteroid and meteorite samples and can provide important context about prebiotic organic compounds. "Beta-alanine is a prominent example of the amazingly diverse collection of amino acid–like molecules found in space samples," said Katherine Freeman, Evan Pugh University Professor, Dr.
Mary Barnes Professor of Geosciences, and the principal investigator on the project. "It can help us understand why there are so many different types of these compounds and where and how they were made. Ultimately, this helps us understand ways that space organics potentially shaped the unique chemistry in life." Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly.
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