NASA scientists have discovered compounds on samples collected from Asteroid Bennu that are precursors to life, demonstrating the importance of Earthbound sample-return missions.
The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) spacecraft collected the groundbreaking samples from the near-Earth asteroid before returning them to Earth in 2023. Intriguingly, the asteroid contained molecules conducive to life and saltwater residue, suggesting a sort of “broth” in which they could interact and combine.
Altering Scientific Understanding of Our Solar System
Analysis of the Bennu samples does not provide evidence of life itself, yet it suggests that the necessary conditions for life could have been commonplace in the early solar system. As future missions investigate the sands of Mars and the oceans of Europa for life, they are now encouraged with a new reason to be hopeful.
“NASA’s OSIRIS-REx mission already is rewriting the textbook on what we understand about the beginnings of our solar system,” said Nicky Fox, associate administrator of NASA’s Science Mission Directorate at the space agency’s headquarters in Washington. “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.”
NASA Discovers Amino Acids on Bennu
All life on Earth is constructed from a pool of only 20 amino acids, 14 of which were found in the Bennu samples. Additionally, the five nucleobases that store and transmit genetic information at the core of DNA and RNA are also all present on Bennu.
Additionally, testing detected a high amount of ammonia and formaldehyde, which can combine into more complex molecules, including amino acids. From complete amino acids to their molecular building blocks, the raw ingredients of life are plentiful on Bennu.
The recent discoveries may not be the first time scientists have found precursors to life on extraterrestrial objects. However, finding them in a sample collected directly from an object in space and returned to Earth under secure conditions demonstrates that distantly formed rocks could carry the ingredients from which life originates.
“The clues we’re looking for are so minuscule and so easily destroyed or altered from exposure to Earth’s environment,” explained NASA’s Danny Glavin, a senior sample scientist at the Goddard Space Flight Center in Greenbelt, Maryland. “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.”
An Ideal Environment For Life According to International Researchers
Beyond Glavin’s work on amino acids, Tim McCoy of the Smithsonian’s Nation Museum of Natural History in Washington and Sara Russell of the Natural History Museum in London analyzed the environment in which those building blocks were found. They uncovered traces of 11 minerals formed through water evaporation, including some, such as the mineral trona, which has never before been discovered from an extraterrestrial source.
The analysis further demonstrated that the salty brine from which the samples arrived took thousands of years to evaporate on Bennu.
Both NASA teams work “really go hand in hand in trying to explain how life’s ingredients actually came together to make what we see on this aqueously altered asteroid,” McCoy said in a statement.
NASA Rethink Amino Acids
The longstanding mystery of why life prefers so-called “left-handed” amino acids also deepened with the Bennu samples. All amino acids occur in mirror versions of each other, like a human’s hands. For some mysterious reason, life prefers left-handed amino acids to right-handed ones.
Many space samples have likewise indicated a higher concentration of left-handed amino acids, suggesting that they were likely more common in the universe and, therefore, more likely to form the building blocks of life. Yet, the Bennu sample, full of pristine building blocks, contains an even split of both types of amino acid compositions.
“This is a big mystery, actually, in the origin of life, you don’t know how this this happened. You can have life using the mirror image form, the right-handed form, and it would function just as well,” Glavin explained.
“The hypothesis had been that the early solar system was biased towards the left-handed version very early on, prior to the origin of life,” Glavin said, “and this is potentially one reason why life evolved to use the left hand.”
“So we were looking forward to studying these vendor samples, hopefully confirming that hypothesis. But that’s not what we found. We found equal mixtures of the left and right-handed forms in these samples,” Glavin said.
“And I have to admit, I was a little disillusioned or disappointed. I felt like this had invalidated 20 years of research in our lab and my career,” Glavin added. “But this is exactly why we explore. This is why we do these missions, right? If we knew everything in advance, we wouldn’t need to do an OSIRIS REx to bring these samples back. So we have plans to study additional samples of Bennu.”
The first of the two papers, “Abundant Ammonia and Nitrogen-Rich Soluble Organic Matter in Samples from Asteroid (101955) Bennu,” appeared on January 29, 2025, in Nature Astronomy. The second paper, “An Evaporite Sequence from Ancient Brine Recorded in Bennu Samples,” appeared on January 29, 2025, in Nature.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.