Scientists have found that molecules of beta-alanine from the asteroid Bennu and from the Murchison meteorite, while formed through the same chemical pathways, have dramatically different isotopic fingerprints at the atomic level, indicating they originated in separate environments within the early solar system. The finding, published in Nature Communications Earth and Environment, suggests that the building blocks of life can form under a wider range of conditions than previously thought.
The research’s lead author was Ophélie Mcintosh, a former postdoctoral researcher at Penn State's Department of Geosciences. It compared beta-alanine, an amino acid not used by Earth organisms to build proteins, in the Bennu sample returned by NASA's OSIRIS-REx mission in 2023 and in the Murchison meteorite.
Using two specialized instruments, a pico-CSIA (Picomolar-scale compound-specific isotope analyses) device unique to Penn State and a modified GC-Orbitrap mass spectrometer, the team measured not just the bulk isotopic composition of the molecules but the isotopic ratios of individual carbon and nitrogen atoms within the same molecule. This intramolecular level of detail is new.
“I was genuinely gobsmacked by the enormous isotope difference between two neighboring atom positions within the same molecule,” said Katherine Freeman, professor of geosciences at Penn State and principal investigator of the project. “The preservation of such startling differences is an indicator of the primordial nature of these molecules. We are working with molecules formed at the very dawn of the solar system, possibly even before the formation of Earth.”
The Bennu sample, collected and preserved in a sterile capsule before being opened in laboratory conditions, is especially valuable scientifically. A sample of the Murchison meteorite sits at the National Museum of Natural History in Washington, D.C.
“When you compare the Bennu and Murchison samples, the carbon isotope average is so close that when you factor in margin of error, they’re basically the same,” Mcintosh said. “But when you look at intramolecular carbon, they’re completely different.”
The authors found that the two samples share a similar intramolecular isotope distribution, consistent with a common synthetic route, but differ markedly in their position-specific carbon and nitrogen isotope compositions. The authors say these differences are hard to reconcile with any known processes inside the parent bodies and instead reflect different chemical pathways in different parts of the protoplanetary disk.
“One of the main things we discovered, for both glycine and beta-alanine, is that they might have formed in different environments or places in the solar system,” Mcintosh said. “This broadens our understanding of the type of environments where you can form those very important molecules for prebiotic chemistry.”
The results could help future missions, including missions to Jupiter's icy moons, search for potential biosignatures. Isotopic analyses of amino acids and other prebiotic molecules provide an abiotic baseline for that search.
“Isotope ratios provide a measurable tag that can link molecules to specific reservoirs or processes,” said paper co-author Christopher House, professor of geosciences at Penn State. “For our study, isotopes provided clues to an older history for specific atoms in a molecule.”
Analysis
Why This Matters
- The finding shows that the same organic building blocks of life can arise in multiple, chemically distinct environments within the early solar system, increasing the likelihood that such molecules are common across planetary systems.
- It provides a new method, intramolecular isotopic analysis, that can trace the formation history of individual molecules back to the protoplanetary disk, offering a far more detailed picture of prebiotic chemistry than bulk measurements.
- The work establishes a crucial "abiotic baseline" for future missions searching for biosignatures on places like Jupiter's moon Europa, helping distinguish molecules produced by life from those formed in space.
Background
NASA's OSIRIS-REx mission collected a sample from the carbonaceous asteroid Bennu in 2020 and returned it to Earth in 2023, making it one of the most pristine extraterrestrial samples ever studied. Earlier analysis of that sample had already revealed the presence of 14 of the 20 amino acids that make up proteins in Earth life, along with four essential building blocks for DNA and RNA. The Murchison meteorite, a carbon-rich meteorite that fell in Australia in 1969, has long been a standard for studying extraterrestrial organic chemistry. This new study goes beyond earlier work by comparing isotopic ratios atom-by-atom within the same molecule.
Key Perspectives
Katherine Freeman (Professor of Geosciences, Penn State): expressed astonishment at the "enormous isotope difference" between neighboring atoms in the same molecule, calling it an indicator of the molecules' primordial nature, formed "at the very dawn of the solar system, possibly even before the formation of Earth."
Ophélie Mcintosh (lead author, former Penn State postdoc): said the discovery that beta-alanine and glycine formed in different environments “broadens our understanding of the type of environments where you can form those very important molecules for prebiotic chemistry.”
Christopher House (co-author, professor of geosciences, Penn State): explained that isotopes provide “a measurable tag that can link molecules to specific reservoirs or processes” and that this study gave clues to “an older history for specific atoms in a molecule.”
What to Watch
- Future isotopic studies of other molecules in the Bennu sample, such as glycine, may reveal similar or contrasting formation environments, further mapping the chemical heterogeneity of the protoplanetary disk.
- Upcoming sample-return missions, including JAXA's MMX to the Martian moon Phobos and NASA's Dragonfly to Titan, may apply these techniques to search for biosignatures with a refined abiotic baseline.
- The development of portable or space-qualified versions of the pico-CSIA and GC-Orbitrap instruments could enable real-time isotopic analysis on future missions to icy moons or other targets.
Checked
12 claims in this story checked against 1 source: 12 supported.
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- SupportedBennu’s sample shows that organic molecules formed in different parts of the early solar system.Universe Today: “This work shows that the same organic molecules can form in different parts of the disk, though with different isotopic compositions.”
- SupportedIsotopic analysis of beta-alanine from Bennu and Murchison suggests the molecules may have formed in distinct environments, broadening the potential range of conditions for prebiotic chemistry.Universe Today: ““This broadens our understanding of the type of environments where you can form those very important molecules for prebiotic chemistry.””
- SupportedBennu and Murchison beta-alanine had dramatically different position-specific isotope fingerprints despite having the same formation pathways, indicating different environments in the early solar system.Universe Today: “The intramolecular isotope differences show that, while their formation pathways were the same, they took place in much different environments, or in different batches.”
- SupportedThe research was published in Nature Communications Earth and Environment, and suggests prebiotic molecules can form under a wider range of conditions than previously thought.Universe Today: “The research is published in Nature Communications Earth and Environment”
- SupportedOphélie Mcintosh was the lead author and a former postdoctoral researcher in Penn State’s Department of Geosciences.Universe Today: “The lead author is Ophélie Mcintosh, a former postdoctoral researcher in Penn State’s Department of Geosciences.”
- SupportedThe team used a Penn State-only pico-CSIA device and a modified GC-Orbitrap to examine bulk and position-specific isotope compositions in beta-alanine.Universe Today: “A device unique to Penn State allowed the measurement of isotopic averages in extremely small samples. It's called pico-CSIA”
- SupportedKatherine Freeman said, “I was genuinely gobsmacked by the enormous isotope difference between two neighboring atom positions within the same molecule.”Universe Today: ““I was genuinely gobsmacked by the enormous isotope difference between two neighboring atom positions within the same molecule,” said project principal investigator Katherine Freeman”
- SupportedFreeman said the preserved isotope differences indicate the molecules are primordial and may have formed before Earth.Universe Today: ““The preservation of such startling differences is an indicator of the primordial nature of these molecules. We are working with molecules formed at the very dawn of the solar system, possibly even before the formation of Earth.””
- SupportedMcintosh said the average carbon isotope values in the two samples are essentially the same within the margin of error, but their intramolecular carbon values differ.Universe Today: ““When you compare the Bennu and Murchison samples, the carbon isotope average is so close that when you factor in margin of error, they’re basically the same,” Mcintosh said. “But when you look at intramolecular carbon, they’re completely different.””
- SupportedThe samples have similar intramolecular isotope distributions consistent with a common synthetic route, but markedly different position-specific carbon and nitrogen isotope compositions.Universe Today: “"The samples display similar intramolecular isotope distributions, consistent with a common synthetic route, but differ markedly in their position-specific carbon and nitrogen isotope compositions," the authors explain.”
- SupportedThe authors say the differences are difficult to reconcile with known processes inside parent bodies and instead reflect different pathways in different parts of the protoplanetary disk.Universe Today: “The authors say that the differences are hard to reconcile with any known processes taking place inside parent bodies. Instead, they reflect different chemical pathways in different parts of the protoplanetary disk.”
- SupportedThe results could help missions to Jupiter’s icy moons search for potential biosignatures, and isotope analyses provide an abiotic baseline for that search.Universe Today: “These results could also be helpful as missions to detect and study potential biosignatures elsewhere in the Solar System are launched. Missions to Jupiter's icy moons could benefit from these results, for example.”