Penn State study ties Bennu amino acids to Murchison meteorite

Researchers at Penn State reported in 2026 that amino acids from asteroid Bennu and the Murchison meteorite may have formed through one process while originating in widely separated parts of the early solar system, in work published in Communications Earth & Environment.

The team compared beta-alanine in both samples and found that the overall carbon isotope average roughly matched within the margin of error, while the intramolecular carbon patterns differed completely. Of the molecule’s three carbons, one is enriched in neutrons and the other two are depleted, though the specific values differ between Bennu and Murchison. Mcintosh said, “Most studies focus on the distribution and quantification of amino acids, so our question about how they’re formed is quite new.”

Bennu’s beta-alanine carried enriched carbon marking the top isotope anomaly ever seen in an organic molecule from space. The team says this extreme gap between enriched and depleted carbons shows the molecules are primordial, dating to the dawn of the solar system. “I was genuinely gobsmacked by the enormous isotope difference between two neighboring atom positions within the same molecule,” said principal investigator Katherine Freeman.

For the measurements, the team used a new intramolecular isotope technique with the pico-CSIA instrument, found only at Penn State, plus a modified GC-Orbitrap that reads isotope composition at different spots inside a molecule. The pico-CSIA handles the amounts of material that rare samples require, while the GC-Orbitrap resolves isotope values for each carbon and nitrogen in beta-alanine.

NASA’s OSIRIS-REx mission delivered the Bennu amino acids to Earth in 2023 as a sample direct from space without terrestrial contamination, while the Murchison meteorite reached Earth in 1969. The team said the uncontaminated Bennu sample showed where the molecules might have formed, unlike meteorites changed by exposure to Earth.

Beta-alanine is not among the 20 amino acids that form proteins, yet it is among the most common amino acids in asteroid and meteorite samples and can combine with others to build peptide enzymes. It is also produced naturally in the human body. Freeman said beta-alanine represents the varied amino-acid-like molecules found in space samples and helps explain how space organics influenced the chemistry of life. The same team’s earlier work found that glycine on Bennu may have emerged in a harsh, cold setting, rejecting the view that they formed in warm, wet settings.

NASA’s OSIRIS-REx mission has concluded, although research on amino acids from asteroid and meteorite samples continues. Freeman said a key next step is to study how space environments and water exposure might change isotope ordering within molecules, work that would help reveal a molecule’s history. McIntosh hopes researchers keep using intramolecular isotope measurement techniques in astronomy and other fields.

An ETH Zurich study published in Science Advances in 2026 concluded that Bennu most likely took shape near the water-ice line, where material from the inner and outer solar system blended, overturning old assumptions that it formed late in the outer solar system. The researchers say water ice served as glue, binding fine dust particles as the solar system formed about 4.5 billion years ago.

Bennu, the asteroid Ryugu, and CI meteorites carry a matching iron, titanium, and chromium isotopic fingerprint, which the researchers say shows the bodies formed from the same reservoir of cosmic dust and differ from other asteroids, meteorite groups, and planets. The team found titanium and iron spread evenly through Bennu’s material as it built this chemical fingerprint.

Jupiter formed within roughly one million years of the Sun’s birth, serving as a barrier that blocked coarse material but let fine dust from different regions blend near the water-ice boundary, where Bennu’s precursors formed. Ice near the water-ice line evaporated, and water vapor condensed again where Bennu formed, helping explain its water-rich material. Jupiter’s gravity left Bennu’s parent material dominated by fine dust that circulated and mixed efficiently through the disk, preserving a composition resembling the Sun.

Bennu is a primordial asteroid, and its material goes back about 4.5 billion years with little change, offering a glimpse of the original elemental mix behind the terrestrial planets. Bennu circles the Sun once every 1.2 years and approaches Earth about every six years, coming within roughly 300,000 kilometers. The asteroid currently lies more than 200 million miles (322 million kilometers) from Earth. The OSIRIS-REx capsule carried approximately 120 grams of Bennu material to a landing in Utah on September 23, 2023, and ETH Zurich received half a gram.

Maria Schönbächler says researchers are now wondering whether other asteroids have the same isotopic signature as Bennu and Ryugu, and it remains unclear how much young Jupiter contributed to fine dust clumping. “We are now wondering whether other asteroids have the same isotopic signature as Bennu and Ryugu,” Schönbächler said.

She plans to apply to JAXA for material from Japan’s Phobos sample-return mission, set to launch at the end of October 2026 and return to Earth in 2031. “It would be exciting to also obtain this material to analyse it in my laboratory,” she said. She hopes to study whether other asteroids share Bennu’s isotopic signature, though Jupiter’s role in dust clumping needs more research.

More asteroid samples could let scientists test the proposed formation scenario and check whether other ancient bodies share Bennu’s chemical signature. Samples from Japan’s Phobos mission could help show how material moved between different regions of the early solar system. ETH Zurich’s findings do not pin down exactly how organics arrived at Earth, yet they show where those ingredients came from and how they moved through the young solar system. Bennu’s samples help scientists reconstruct the conditions before Earth and the other rocky planets finished forming.