Astrochemistry

Dust From asteroid Bennu: Building Blocks Of Life And Possible Habitats Were Widespread In Our Solar System

By Keith Cowing

Press Release

Goethe University Frankfurt

January 30, 2025

Filed under amino acid, asteroid, astrochemistry, astrogeology, Bennu, biochemistry, Biosignatures, brine, DNA, Goethe University Frankfurt, habitability, nucleoside, organic chemistry, OSIRIS-REx, protein, RNA, Sample Return

Dust From asteroid Bennu: Building Blocks Of Life And Possible Habitats Were Widespread In Our Solar System — a, Summed mass spectrum acquired from several ~100 μm grains mounted on a KBr window with mass peaks for ammonia (NH3), sodium (Na), formaldehyde (H2C=O), hydrogen sulfide (H2S) and potassium (K) indicated. Spectrum acquired by μ-L2MS using a vacuum UV photoionization at 118 nm. b, Optical mosaic of particle with yellow box demarking region mapped by μ-L2MS. c, Spatial map of ammonia distribution overlaid over optical image. The μ-L2MS laser beam spot size was 5 μm. — Nature Astronomy

It took two years for NASA’s OSIRIS-REx space probe to return from asteroid Bennu before dropping off a small capsule as it flew past Earth, which was then recovered in the desert of the U.S. state of Utah on September 24, 2023. Its contents: 122 grams of dust and rock from asteroid Bennu.

The probe had collected this sample from the surface of the 500-metre agglomerate of unconsolidated material in a touch-and-go maneuver that took just seconds. Since the capsule protected the sample from the effects of the atmosphere, it could be analyzed in its original state by a large team of scientists from more than 40 institutions around the world.

The partners in Germany were geoscientists Dr. Sheri Singerling, Dr. Beverley Tkalcec and Prof. Frank Brenker from Goethe University Frankfurt. They examined barely visible grains of Bennu using the transmission electron microscope of the Schwiete Cosmochemistry Laboratory, set up at Goethe University only a year ago with the support of the Dr. Rolf M. Schwiete Foundation, the German Research Foundation and the State of Hesse.

Its goal: to reconstruct the processes that took place on Bennu’s protoplanetary parent body more than four billion years ago and ultimately led to the formation of the minerals that exist today. The Frankfurt scientists succeeded in doing this by analyzing the mineral grains’ exact structure and determining their chemical composition at the same time. They also carried out trace element tomography of the samples at accelerators such as DESY (Deutsches Elektronen-Synchrotron) in Hamburg.

The Bennu samples contain amino acids — the building blocks of proteins — including 14 of the 20 that life uses to create proteins here on Earth. In addition, the samples contain all five of the nucleobases that encode genetic information in DNA and RNA. — NASA

“Together with our international partner teams, we have been able to detect a large proportion of the minerals that are formed when salty, liquid water – known as brine – evaporates more and more and the minerals are precipitated in the order of their solubility,” explains Dr. Sheri Singerling, who manages the Schwiete Cosmo Lab. In technical terms, the rocks that form from such precipitation cascades are called evaporites. They have been found on Earth in dried-out salt lakes, for example.

“Other teams have found various precursors of biomolecules such as numerous amino acids in the Bennu samples,” reports Prof. Frank Brenker. “This means that Bennu’s parent body had some known building blocks for biomolecules, water and – at least for a certain time – energy to keep the water liquid.” However, the break-up of Bennu’s parent body interrupted all processes very early on and the traces that have now been discovered were preserved for more than 4.5 billion years.

“Other celestial bodies such as Saturn’s moon Enceladus, or the dwarf planet Ceres have been able to evolve since then and are still very likely to have liquid oceans or at least remnants of them under their ice shells,” says Brenker. “Since this means that they have a potential habitat, the search for simple life that could have evolved in such an environment is a focus of future missions and sample studies.”

a, Mass spectra of Bennu (black) and Ryugu (orange) samples showing the relative abundance of polythionates with three to seven S atoms. b, Detail around m/z = 319 with major annotated elementary compositions (complete annotation can be found in Supplementary Fig. 3). c–e, Data visualization of the chemical compositions and number of molecules in Bennu (c) compared with Ryugu (d) and Murchison (e). Top, the Van Krevelen diagrams of H/C versus O/C atomic ratios of the compositional data as obtained from exact mass analysis. Coloured annuli enclose the total number of molecules assigned by mass, with colours indicating the relative abundances of the chemical families. Individual data points use the same colours to specify each family, and the size of each bubble reflects the intensity of the signal from the mass spectrum. Middle, the H/C atomic ratios as a function of m/z from 100 to 700. Bottom, the number of molecular formulae as a function of number of oxygen atoms in the CHO, CHOS and CHNO chemical families. — Nature Astronomy

OSIRIS-REx

NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provided overall mission management, systems engineering, and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator. The university leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and provided flight operations.

Background information

Daniel P. Glavin et al.: Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu Nature Astronomy (2025) (open access)