Scientists Find Amino Acids, Salts and Other Compounds in Samples from Asteroid Bennu

Asteroid Bennu is thought to be made of rubble fragments from a 4.5-billion-year-old parent body, containing materials that originated beyond Saturn, which was destroyed long ago in a collision with another object. In two new papers, scientists report the detection of amino acids (including 14 of the 20 used in terrestrial biology), polycyclic aromatic hydrocarbons, ammonia and other compounds, as well as a variety of salts, including sodium carbonates, phosphates, sulfates, and chlorides, in the Bennu samples, which NASA’s OSIRIS-REx spacecraft delivered to Earth in 2023.

“NASA’s OSIRIS-REx mission already is rewriting the textbook on what we understand about the beginnings of our Solar System,” said Dr. Nicky Fox, associate administrator for Science Mission Directorate at NASA Headquarters.

“Asteroids provide a time capsule into our home planet’s history, and Bennu’s samples are pivotal in our understanding of what ingredients in our Solar System existed before life started on Earth.”

In the Bennu samples, the researchers found amino acids — 14 of the 20 that life on Earth uses to make proteins — and all five nucleobases that life on Earth uses to store and transmit genetic instructions in more complex terrestrial biomolecules, such as DNA and RNA, including how to arrange amino acids into proteins.

They also detected exceptionally high abundances of ammonia, which is important to biology because it can react with formaldehyde, which also was detected in the samples, to form complex molecules, such as amino acids — given the right conditions.

When amino acids link up into long chains, they make proteins, which go on to power nearly every biological function.

These building blocks for life detected in the Bennu samples have been found before in extraterrestrial rocks.

However, identifying them in a pristine sample collected in space supports the idea that objects that formed far from the Sun could have been an important source of the raw precursor ingredients for life throughout the Solar System.

“The clues we’re looking for are so minuscule and so easily destroyed or altered from exposure to Earth’s environment,” said Dr. Danny Glavin, a senior sample scientist at NASA’s Goddard Space Flight Center.

“That’s why some of these new discoveries would not be possible without a sample-return mission, meticulous contamination-control measures, and careful curation and storage of this precious material from Bennu.”

The scientists identified traces of 11 salt minerals in the Bennu samples that form as water containing dissolved salts evaporates over long periods of time, leaving behind the salts as solid crystals.

Similar brines have been detected or suggested across the Solar System, including at the dwarf planet Ceres and Saturn’s moon Enceladus.

“The discovery of these salts was a breakthrough in space research,” said Dr. Nick Timms, a researcher at Curtin University.

“We were surprised to identify the mineral halite, which is sodium chloride — exactly the same salt that you might put on your chips.”

“The minerals we found form from evaporation of brines — a bit like salt deposits forming in the salt lakes that we have in Australia and around the world.”

“By comparing with mineral sequences from salt lakes on Earth, we can start to envisage what it was like on the parent body of asteroid Bennu, providing insight into ancient cosmic water activity.”

“OSIRIS-REx has been a highly successful mission,” said OSIRIS-REx project scientist Dr. Jason Dworkin, a researcher at NASA’s Goddard Space Flight Center.

“The OSIRIS-REx data add major brushstrokes to a picture of a solar system teeming with the potential for life.”

“Why we, so far, only see life on Earth and not elsewhere, that’s the truly tantalizing question.”

The findings appear in two papers in the journal Nature Astronomy and the journal Nature.

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D.P. Glavin et al. Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu. Nat Astron, published online January 29, 2025; doi: 10.1038/s41550-024-02472-9

T.J. McCoy et al. 2025. An evaporite sequence from ancient brine recorded in Bennu samples. Nature 637, 1072-1077; doi: 10.1038/s41586-024-08495-6