NASA’s OSIRIS-REx mission delivered samples from asteroid Bennu, revealing crucial molecules linked to life, including amino acids and nucleobases found in DNA and RNA. The presence of ammonia and formaldehyde suggests conditions ripe for forming complex molecules in space.
Scientists also discovered a suite of evaporite minerals, indicating Bennu once had water-rich environments that could have supported prebiotic chemistry. The mission highlights the widespread potential for life’s building blocks across the solar system, leaving open the question of why Earth remains the only known host of life.
Asteroid Bennu’s Secrets: Ingredients for Life?
NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification and Security–Regolith Explorer) spacecraft has brought back rock and dust samples from asteroid Bennu, revealing molecules essential for life on Earth. Scientists also found evidence of ancient saltwater, which could have served as the “broth” that helped these molecules interact and evolve into more complex compounds.
While the findings do not show evidence for life itself, they suggest that the early solar system had the right conditions for life to emerge, making it more likely that life could have formed on other planets and moons.
“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, Science Mission Directorate at NASA 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.”
The origin of life is one of the deepest mysteries in science, but the clues to solving it have been buried by plate tectonics, the water cycle, and even life itself. For answers, scientists are looking beyond Earth to primitive asteroids like Bennu, the target of NASA’s daring OSIRIS-REx sample return mission. OSIRIS-REx gathered pristine material from Bennu in 2020 and delivered it to Earth in 2023. Now, rocks from Bennu are revealing a lost world from the dawn of the solar system, with the right conditions to foster the building blocks of life. Credit: NASA’s Goddard Space Flight Center
Unveiling Life’s Building Blocks in Space
In research papers published in the journals Nature and Nature Astronomy, scientists from NASA and other institutions shared results of the first in-depth analyses of the minerals and molecules in the Bennu samples, which OSIRIS-REx delivered to Earth in 2023.
Detailed in the Nature Astronomy paper, among the most compelling detections were 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.
Scientists also described exceptionally high abundances of ammonia in the Bennu samples. Ammonia 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.
A Pristine Sample, Untouched by Earth
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 Danny Glavin, a senior sample scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-lead author of the Nature Astronomy paper. “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.”
Tracing Bennu’s Watery Past
While Glavin’s team analyzed the Bennu samples for hints of life-related compounds, their colleagues, led by Tim McCoy, curator of meteorites at the Smithsonian’s National Museum of Natural History in Washington, and Sara Russell, cosmic mineralogist at the Natural History Museum in London, looked for clues to the environment these molecules would have formed. Reporting in the journal Nature, scientists further describe evidence of an ancient environment well-suited to kickstart the chemistry of life.
Ranging from calcite to halite and sylvite, scientists identified traces of 11 minerals in the Bennu sample 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.
A Complete Set of Minerals Never Seen Before
Although scientists have previously detected several evaporites in meteorites that fall to Earth’s surface, they have never seen a complete set that preserves an evaporation process that could have lasted thousands of years or more. Some minerals found in Bennu, such as trona, were discovered for the first time in extraterrestrial samples.
“These papers 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,” said McCoy.
Unlocking the Mystery of Life’s Left-Handed Bias
For all the answers the Bennu sample has provided, several questions remain. Many amino acids can be created in two mirror-image versions, like a pair of left and right hands. Life on Earth almost exclusively produces the left-handed variety, but the Bennu samples contain an equal mixture of both. This means that on early Earth, amino acids may have started out in an equal mixture, as well. The reason life “turned left” instead of right remains a mystery.
A Universe Full of Potential—But Why Only Earth?
“OSIRIS-REx has been a highly successful mission,” said Jason Dworkin, OSIRIS-REx project scientist at NASA Goddard and co-lead author on the Nature Astronomy paper. “Data from OSIRIS-REx adds 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.”
Explore Further: Scientists Just Found DNA’s Building Blocks in Asteroid Bennu
References:
- “Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu” by Daniel P. Glavin, Jason P. Dworkin, Conel M. O’D. Alexander, José C. Aponte, Allison A. Baczynski, Jessica J. Barnes, Hans A. Bechtel, Eve L. Berger, Aaron S. Burton, Paola Caselli, Angela H. Chung, Simon J. Clemett, George D. Cody, Gerardo Dominguez, Jamie E. Elsila, Kendra K. Farnsworth, Dionysis I. Foustoukos, Katherine H. Freeman, Yoshihiro Furukawa, Zack Gainsforth, Heather V. Graham, Tommaso Grassi, Barbara Michela Giuliano, Victoria E. Hamilton, Pierre Haenecour, Philipp R. Heck, Amy E. Hofmann, Christopher H. House, Yongsong Huang, Hannah H. Kaplan, Lindsay P. Keller, Bumsoo Kim, Toshiki Koga, Michael Liss, Hannah L. McLain, Matthew A. Marcus, Mila Matney, Timothy J. McCoy, Ophélie M. McIntosh, Angel Mojarro, Hiroshi Naraoka, Ann N. Nguyen, Michel Nuevo, Joseph A. Nuth III, Yasuhiro Oba, Eric T. Parker, Tanya S. Peretyazhko, Scott A. Sandford, Ewerton Santos, Philippe Schmitt-Kopplin, Frederic Seguin, Danielle N. Simkus, Anique Shahid, Yoshinori Takano, Kathie L. Thomas-Keprta, Havishk Tripathi, Gabriella Weiss, Yuke Zheng, Nicole G. Lunning, Kevin Righter, Harold C. Connolly Jr. and Dante S. Lauretta, 29 January 2025, Nature Astronomy.
DOI: 10.1038/s41550-024-02472-9 - “An evaporite sequence from ancient brine recorded in Bennu samples” by T. J. McCoy, S. S. Russell, T. J. Zega, K. L. Thomas-Keprta, S. A. Singerling, F. E. Brenker, N. E. Timms, W. D. A. Rickard, J. J. Barnes, G. Libourel, S. Ray, C. M. Corrigan, P. Haenecour, Z. Gainsforth, G. Dominguez, A. J. King, L. P. Keller, M. S. Thompson, S. A. Sandford, R. H. Jones, H. Yurimoto, K. Righter, S. A. Eckley, P. A. Bland, M. A. Marcus, D. N. DellaGiustina, T. R. Ireland, N. V. Almeida, C. S. Harrison, H. C. Bates, P. F. Schofield, L. B. Seifert, N. Sakamoto, N. Kawasaki, F. Jourdan, S. M. Reddy, D. W. Saxey, I. J. Ong, B. S. Prince, K. Ishimaru, L. R. Smith, M. C. Benner, N. A. Kerrison, M. Portail, V. Guigoz, P.-M. Zanetta, L. R. Wardell, T. Gooding, T. R. Rose, T. Salge, L. Le, V. M. Tu, Z. Zeszut, C. Mayers, X. Sun, D. H. Hill, N. G. Lunning, V. E. Hamilton, D. P. Glavin, J. P. Dworkin, H. H. Kaplan, I. A. Franchi, K. T. Tait, S. Tachibana, H. C. Connolly Jr. and D. S. Lauretta, 29 January 2025, Nature.
DOI: 10.1038/s41586-024-08495-6
OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) is a NASA spacecraft designed to study and collect samples from the near-Earth asteroid Bennu. Managed by NASA’s Goddard Space Flight Center, OSIRIS-REx was developed as part of NASA’s New Frontiers Program, overseen by the Marshall Space Flight Center. The mission’s principal investigator, Dante Lauretta of the University of Arizona, leads the science team, observation planning, and data processing.
The spacecraft was built and operated by Lockheed Martin Space, while KinetX Aerospace and NASA Goddard handled navigation. The mission also includes international collaborations, such as the OSIRIS-REx Laser Altimeter from the Canadian Space Agency (CSA) and scientific cooperation with JAXA’s Hayabusa2 asteroid mission. After successfully collecting samples from Bennu, OSIRIS-REx returned them to Earth for study, with curation taking place at NASA’s Johnson Space Center in Houston.
