Bennu Asteroid Sample Reveals Huge Isotope Gap Inside One Molecule

A new study of asteroid Bennu's sample has turned up a surprise inside a single molecule, according to Universe Today. Researchers at Penn State measured the carbon in a molecule called beta-alanine from Bennu and from the Murchison meteorite, and they found a large difference between two neighboring atom positions in the same molecule.

The work, published in Nature Communications Earth and Environment, offers a more detailed look at how the building blocks of life may have formed in the early Solar System.

What the researchers did

NASA's OSIRIS-REx mission returned the Bennu sample in 2023. Earlier examination of the material found 14 of the 20 amino acids that make up proteins in Earth life, along with four of the essential building blocks for DNA and RNA.

In the new study, the team compared one molecule, beta-alanine, in Bennu's material with the same molecule from the Murchison meteorite. Beta-alanine is not used by Earth organisms to build proteins, but it does play other roles in terrestrial life. Finding it in rocks from space is interesting because it can offer insight into prebiotic chemistry and the conditions in the very early Solar System.

The lead author is Ophélie Mcintosh, a former postdoctoral researcher in Penn State's Department of Geosciences. The paper is titled “Nitrogen and intramolecular carbon isotopic measurements of β-alanine in samples from asteroid Bennu and the Murchison meteorite.”

A finer isotopic fingerprint

Most earlier work on amino acids in meteorites and asteroid samples has focused on what is present and how much. Mcintosh said in a press release that the question of how these molecules form is quite new. Rather than comparing only overall compositions, the team measured differences among carbon atoms within the same molecule, a level of detail Universe Today described as new.

Two instruments made this possible. One is a device that exists only at Penn State, called pico-CSIA, which measures isotopic averages in extremely small samples. The other is a modified gas chromatography-Orbitrap mass spectrometer, which measured the composition at specific positions inside beta-alanine molecules.

Mcintosh said this position-specific information gives a much more detailed isotopic fingerprint, one that can help tell apart possible formation pathways. Christopher House, a Penn State professor of geosciences and a co-author, said isotope ratios act as a measurable tag that can link molecules to particular reservoirs or processes. In this study, he said, the isotopes gave clues to an older history for specific atoms in a molecule.

Katherine Freeman, a Penn State professor of geosciences, said she was “genuinely gobsmacked” by the enormous isotope difference between two neighboring atom positions in the same molecule.

Why it matters

The finding does not show that life exists elsewhere. Its importance is in what it adds to the picture of where life's ingredients come from. Universe Today noted that discoveries of amino acids on asteroids and comets suggest that some precursors of life could be widespread in the Solar System, and possibly in other planetary systems.

Bennu's sample is especially valuable because it was collected and kept in a sterile capsule before being opened under laboratory conditions. The authors write that it offers a chance to study amino acids in pristine material unaffected by contamination on Earth.

Scientists hoped that new laboratory techniques would be developed in the years between planning the mission and getting the sample in hand. In this case, Universe Today reported, that is what happened.

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Around Prague, based on reporting by Universe Today

Cover photo: NASA/Goddard/University of Arizona/Lockheed Martin / Wikimedia Commons (public domain)