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Life in space? Asteroid Bennu Holds Secrets About The Origin of Life!


Images taken by the OSIRIS-REx spacecraft show Bennu from a distance of about 50 miles (80 kilometers). Credit: NASA/Goddard/University of Arizona, Public Domain


In recent days, groundbreaking discoveries about the asteroid Bennu have yielded new clues about the chemistry of the early solar system and the possible existence of extraterrestrial environments capable of sustaining chemical reactions essential for life.


The OSIRIS-REx mission, which returned intact samples of the asteroid to Earth, enabled detailed analyses that revealed the presence of salts formed from ancient brines and a wide variety of organic compounds, including amino acids and nucleobases essential for DNA and RNA.

The OSIRIS-REx Touch-and-Go sample acquisition mechanism collected more than 120 grams of regolith from the asteroid Bennu. Credit: NASA/Goddard/Erika Blumenfeld and Joseph Aebersold, public domain


These discoveries not only reinforce the theory that compounds essential for life may have formed in space, but also indicate that similar processes may be occurring on other celestial bodies, raising the possibility of habitable environments beyond Earth.


One of the most significant findings in the Bennu samples was the presence of various salts, such as sodium phosphates, sodium-rich carbonates, sulfates, chlorides and fluorides.


These minerals are typical of environments where water-rich fluids evaporate or freeze, processes that occur in closed basins on Earth and have also been detected on icy bodies in the Solar System, such as Ceres and Enceladus.


The formation of these salts indicates that early in Bennu’s history, its parent body contained enough liquid water to generate concentrated brines, an environment that may have favored the synthesis of complex chemical compounds.


The analysis of these samples was only possible because they were carefully collected and stored before any terrestrial contamination.


Unlike meteorites that fall to Earth and are exposed to our atmosphere and biosphere, the materials from Bennu arrived intact, preserving crucial chemical information about their origin and history.

NASA researchers extract a small portion of their regolith sample to prepare “Bennu tea.” Credit: NASA Goddard/OSIRIS-REx, Public Domain


This level of preservation allows scientists to study the processes that occurred in the early solar system without the interference caused by exposure to the terrestrial environment.


In addition to salts, the asteroid samples revealed a surprising abundance of organic compounds, surpassing even those found on the asteroid Ryugu by 75 times, and in many carbonaceous meteorites already studied.


The compounds detected include ammonia, formaldehyde, carboxylic acids, polycyclic aromatic hydrocarbons, and a wide variety of amino acids, including 14 of the 20 used in terrestrial biology.

This energy-dispersive spectrometry map of an unprepared grain of Bennu regolith shows the emplacement of briny salt on clayey materials. Phosphorus is shown in green, calcium in red, iron in yellow and magnesium in blue. A 0.1 millimetre-thick vein of sodium magnesium phosphate (green cluster in centre) formed by evaporation. The phosphate may have played a role in the formation of organic molecules found in the samples. Credit: Natural History Museum, London/Tobias Salge and NASA’s Goddard Space Flight Centre, Public Domain


More impressively, all five nucleobases present in DNA and RNA were identified, suggesting that Bennu may have carried key ingredients for the origin of life.


The scientists also analysed the isotopic signatures of the nitrogen found in these molecules and found that they formed in extremely cold conditions, likely in an interstellar molecular cloud or the outer protoplanetary disk of the solar system.


This suggests that the building blocks of life may have formed even before the formation of planets, being incorporated into asteroids like Bennu and eventually delivered to Earth by impacts.


Another intriguing detail is that the amino acids found in the samples did not show a preferential chirality, that is, there was no predominance of "right-handed" or "left-handed" molecules, unlike what occurs in terrestrial life, where the amino acids used by organisms follow a left-handed pattern.


This raises the question of when and how this asymmetry arose, suggesting that the molecular organization of life may have been influenced by later factors, such as chemical interactions on the early Earth.

Distribution and total abundances of amines, amino acids, and carboxylic acids on Bennu (OREX-803001-0) compared to other asteroids such as Ryugu (A0106) and carbonaceous chondrites (CCs), a type of primitive meteorite rich in organic compounds that fell to Earth naturally. Relative percentages of amines (orange), amino acids (green), and carboxylic acids (blue) are provided in individual pie charts with their overall size proportional to the sum total of the abundances of the three classes of soluble organic compounds.


The findings on Bennu provide a fascinating parallel to other Solar System bodies that exhibit signs of chemical activity in watery environments.


Spectroscopic signals indicate the presence of sodium carbonate on the surface of Ceres and in the plumes of Enceladus, suggesting that brines similar to those that formed the salts on Bennu may still be present on these worlds.


If these watery environments existed long enough and under the right conditions, they could have allowed progressively more complex chemical reactions to occur, potentially leading to the emergence of self-replicating molecules, a key step toward the origin of life.


While there is no direct evidence of life in these locations, the discovery of organic-rich molecules on Bennu reinforces the idea that prebiotic chemistry may be a common phenomenon in the universe.

Rocks from the asteroid Bennu photographed by NASA’s OSIRIS-REx spacecraft. Source: NASA


Study of the Bennu samples has yielded stunning insights into the chemical complexity present in asteroids and reinforced the hypothesis that the essential ingredients for life may be distributed widely throughout space.


The presence of salts formed by brines and the abundance of organic compounds suggests that water-rich environments and complex chemistry may have been more common in the early Solar System than previously thought.


These discoveries expand our understanding of the origins of life and raise new questions about where else these processes may be occurring. If the fundamental building blocks of life can form on asteroids, it is possible that similar systems exist on exoplanets, icy moons, and even other as-yet-unexplored asteroids.


With technology advancing and new space missions planned to investigate ocean worlds like Enceladus and Europa, we are getting closer to answering one of humanity's biggest questions: is life a phenomenon unique to Earth or a common occurrence in the universe?



READ MORE:


An evaporite sequence from ancient brine recorded in Bennu samples.

McCoy, T.J., Russell, S.S., Zega, T.J. et al. 

Nature 637, 1072–1077 (2025). 


Abstract:


Evaporation or freezing of water-rich fluids with dilute concentrations of dissolved salts can produce brines, as observed in closed basins on Earth1 and detected by remote sensing on icy bodies in the outer Solar System2,3. The mineralogical evolution of these brines is well understood in regard to terrestrial environments4, but poorly constrained for extraterrestrial systems owing to a lack of direct sampling. Here we report the occurrence of salt minerals in samples of the asteroid (101955) Bennu returned by the OSIRIS-REx mission5. These include sodium-bearing phosphates and sodium-rich carbonates, sulfates, chlorides and fluorides formed during evaporation of a late-stage brine that existed early in the history of Bennu’s parent body. Discovery of diverse salts would not be possible without mission sample return and careful curation and storage, because these decompose with prolonged exposure to Earth’s atmosphere. Similar brines probably still occur in the interior of icy bodies Ceres and Enceladus, as indicated by spectra or measurement of sodium carbonate on the surface or in plumes2,3.



Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu.

Glavin, D.P., Dworkin, J.P., Alexander, C.M.O. et al.  

Nat Astron (2025). 


Abstract:


Organic matter in meteorites reveals clues about early Solar System chemistry and the origin of molecules important to life, but terrestrial exposure complicates interpretation. Samples returned from the B-type asteroid Bennu by the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer mission enabled us to study pristine carbonaceous astromaterial without uncontrolled exposure to Earth’s biosphere. Here we show that Bennu samples are volatile rich, with more carbon, nitrogen and ammonia than samples from asteroid Ryugu and most meteorites. Nitrogen-15 isotopic enrichments indicate that ammonia and other N-containing soluble molecules formed in a cold molecular cloud or the outer protoplanetary disk. We detected amino acids (including 14 of the 20 used in terrestrial biology), amines, formaldehyde, carboxylic acids, polycyclic aromatic hydrocarbons and N-heterocycles (including all five nucleobases found in DNA and RNA), along with ~10,000 N-bearing chemical species. All chiral non-protein amino acids were racemic or nearly so, implying that terrestrial life’s left-handed chirality may not be due to bias in prebiotic molecules delivered by impacts. The relative abundances of amino acids and other soluble organics suggest formation and alteration by low-temperature reactions, possibly in NH3-rich fluids. Bennu’s parent asteroid developed in or accreted ices from a reservoir in the outer Solar System where ammonia ice was stable.

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