Imagine holding a piece of history older than Earth itself, a fragment of the building blocks that shaped our solar system and, possibly, the origins of life. NASA’s OSIRIS-REx mission has done just that. This ambitious spacecraft returned with samples from asteroid Bennu in late 2023, and the subsequent research in 2024 has revealed profound insights into the universe’s ancient chemistry and our place within it.
OSIRIS-REx, an acronym for Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer, was designed to study Bennu, a near-Earth asteroid with an abundance of organic material. The mission launched in 2016, with the spacecraft reaching Bennu in 2018. Over two years, it meticulously mapped the asteroid, using advanced remote sensing technologies to understand its surface, composition, and geological features. The mission’s highlight came on October 20, 2020, when it successfully collected samples from Bennu’s surface and returned to Earth on September 24, 2023, landing in Utah.
Two days after a Touch-and-Go event (TAG) on the asteroid, the mission team received images that confirmed the spacecraft had collected at least 2 ounces (60 grams) of the asteroid’s surface material. Dr. Thomas Zurbuchen NASA’s associate administrator for science announced with delight, “We are so excited to see what appears to be an abundant sample that will inspire science for decades beyond this historic moment.”
Know about Bennu: A Time Capsule of the Early Solar System
Bennu is more than just a rock in space; it’s a pristine remnant of the solar system, preserved in its unaltered state for billions of years. Unlike Earth, where plate tectonics and weather have erased traces of early history, Bennu’s surface offers a rare glimpse into the chaotic era when planets formed. Scientists chose this asteroid because it is rich in carbon-based compounds, the essential ingredients for life as we know it. Its well-preserved regolith (loosely bound surface dust) could hold molecular clues to the origin of water and organic materials on Earth. Moreover, Bennu’s orbit—close enough to Earth for a feasible mission—made it an ideal candidate for sample return.
Why does it matter? Bennu’s material provides an unprecedented opportunity to analyze astromaterials in laboratories on Earth, bridging the gap between remote observations and tangible evidence. The mission enables scientists to study Bennu’s history, its role as a potential delivery system of organic compounds to Earth, and how space weathering has shaped its regolith. Such analyses promise to fuel discoveries for decades, shedding light on the origins of life and the dynamic processes that govern our solar system.
Asteroids and the Theory of Panspermia
These potential clues to the origin of life naturally lead to the broader question of how life itself may have spread across the Universe. This brings us to the fascinating concept of “panspermia”, the hypothesis that life exists throughout the Universe and is distributed by space dust, asteroids or comets. In simpler terms, panspermia suggests that the seeds of life may have been scattered throughout the cosmos, transported from one celestial body to another.
A series of astronomical observations conducted between 1980 and 2018 align with the theory of cometary panspermia. The key findings include (1) ultraviolet and infrared spectra of interstellar dust, (2) near and mid-infrared spectra of comets, (3) the discovery of an amino acid and degradation products associated with biology from material collected during the Stardust Mission in 2009, (4) jets from Comet Lovejoy that contain both sugar and ethyl alcohol, and (5) data from the Rosetta Mission.
Analyzing the returned sample will allow scientists to study the composition of these organic molecules in detail, potentially revealing whether they possess the chirality (a property of asymmetry in molecules) associated with terrestrial life. This could provide compelling evidence supporting the role of asteroids in delivering the ingredients for life on Earth, and possibly elsewhere in the universe.
The sample capsule pierced through Earth’s atmosphere and floated down gently into the rugged desert terrain of Utah. After years of careful planning, months of specialized training, and countless rehearsals, the NASA recovery team swooped in by helicopter to retrieve the capsule and its valuable contents. To keep it safe from Earth’s environment, the capsule stayed sealed until it was securely transported to a clean room for decontamination. Contrary to expectations, the initial findings were unexpected. No, there weren’t any alien tentacles creeping out from the sample.
After opening the lid, 70 grams of bonus sample containing dark grey rocks and dust outside the sample canister were revealed. To preserve its pure state, the whole operation had to be performed inside a nitrogen-purged glovebox—an enclosed box with built-in gloves that is constantly flooded with neutral nitrogen gas to ensure the sample does not react with other gases in Earth’s atmosphere, like oxygen or water vapor.
Three and a half months after the return capsule touched down on Earth, the curation team was finally able to access the material inside the canister. Another 51g of pristine Bennu material was revealed, and when combined with the bonus rocks and dust already collected, the total amounted to at least 121.6 g, more than twice what the mission had aimed to bring back to Earth.
This material was then cataloged and divided into smaller samples. Up to a quarter of the sample will be distributed to 233 scientists worldwide, who are part of the analysis team that will have the opportunity to study pieces of asteroid firsthand. The remaining 70 percent will be preserved at NASA’s Johnson Space Center for scientists who are not part of the mission team and for future generations to study.
Methods for Sample Analysis
The OSIRIS-REx team has prepared a 274-page document outlining 70 hypotheses to test and specifying the sample amounts down to the milligram. One of the techniques mentioned is spectroscopy, which enables researchers to identify the molecules and compounds that make up the sample. It will help them understand the composition of the asteroid Bennu.
Additionally, microscopy will be employed to reveal the sample’s structure on a small scale. Another important method is spectrometry, which can determine the ratio of isotopes in the sample. This means it can identify the amount of atoms of an element that has extra neutrons in its nucleus, making them heavier. Measuring the ratio of normal atoms to heavier isotopes is incredibly valuable, as it can provide insights into where in the solar system an object formed, whether it contains pre-solar material (material that existed before the sun formed), and how old the object is.
Key Discoveries from Bennu’s Samples
Carbon Abundance
Bennu’s samples revealed a substantial presence of carbon, making up about 4.5–4.7% by weight. This finding highlights the asteroid’s carbonaceous nature, similar to early solar system materials. Among the organic components found are nano globules and polycyclic aromatic hydrocarbons (PAHs), which have preserved their original characteristics without much thermal alteration.
Other elements found were presolar carbides and graphite, further supporting the idea that Bennu has remained largely unchanged since its formation in the protoplanetary disk. These discoveries affirm that Bennu acts as a time capsule, holding clues to the solar system’s earliest building blocks.
Water-Bearing Minerals
The samples showed a significant amount of hydrated minerals, especially phyllosilicates like serpentine and smectite, containing hydration levels of 0.84–0.95% by weight. Spectral analysis confirmed the presence of OH-/H2O and Mg-OH features, pointing to Bennu’s history of aqueous alteration. This hydration is consistent with Bennu’s classification as one of the more aqueously altered carbonaceous chondrites.
The interaction between the asteroid’s minerals and water likely is significant in forming other compounds, such as carbonates, magnetite, and iron sulfides. These hydrated minerals suggest that Bennu had a wet and dynamic past, potentially tied to the evolution of its parent body or its interactions with the protoplanetary disk.
A Surprising Discovery of Phosphates
One of the most unexpected findings was the detection of water-soluble phosphates, including Mg-phosphates and Ca-phosphates. These minerals, which had not been previously identified from spacecraft data, indicate a complex fluid chemistry that could have introduced unique chemical signatures into Bennu’s regolith. The Mg-phosphates, characterized by a nanoporous texture, may serve as important carriers of water and sodium in primitive asteroids, representing a new class of hydrated minerals.
Their composition and structure are similar to findings from asteroid Ryugu, suggesting shared processes in the early solar system. The presence of these phosphates hints at Bennu’s possible connection to a wetter parent body and underscores its importance in understanding the role of water in shaping both organic and inorganic materials in the solar system.
Bennu and Ryugu: A Comparative Exploration
Bennu and Ryugu, two carbon-rich near-Earth asteroids that were investigated by OSIRIS-REx and Hayabusa 2 missions respectively, have some very fascinating similarities that provide an insight into their common origins. Both asteroids have a shape reminiscent of a spinning top, which scientists believe is the result of fragments coming together after a larger parent body breaks apart in a cataclysmic event.
Their compositions are abundant in organic materials and water-bearing minerals, reinforcing their status as some of the most primitive bodies in our solar system. These shared traits suggest that Bennu and Ryugu likely came from the same disrupted parent asteroid in the asteroid belt, and they may have played a role in delivering essential prebiotic materials, like amino acids and nucleobases, to Earth.
Even though they may share a lineage, Bennu and Ryugu have taken different evolutionary routes. Ryugu shows lower levels of hydration, which points to either a greater loss of volatile substances or more intense thermal changes compared to Bennu.
Their surface features also reveal some key differences: Ryugu has a darker, rockier surface with less weathered regolith, while Bennu’s surface is smoother, featuring a blend of fine regolith and boulders. These distinctions might stem from variations in their exposure to solar radiation, thermal cycles, and impacts from micrometeorites.
The discovery of prebiotic molecules further emphasizes their shared background while also highlighting their unique histories. For example, samples from Ryugu showed uracil, a crucial RNA nucleobase, and nicotinic acid, with variations in concentrations across different sample sites possibly linked to exposure to cosmic rays. In contrast, Bennu’s organic content is yet to be revealed.
Looking Ahead: OSIRIS-APEX
The exploration of Bennu and Ryugu has opened new pathways for asteroid research with NASA’s OSIRIS-APEX mission set to investigate another asteroid, Apophis, during its close approach to Earth in 2029. Although we cannot collect regolith samples from Apophis as we did with Bennu, the OSIRIS mission will continue to use its advanced remote sensing suite to analyze the asteroid’s surface geology, which is incredibly powerful.
Concluding with the words of OSIRIS-REx principal investigator Dr. Dante Lauretta, “The bounty of carbon-rich material and the abundant presence of water-bearing clay minerals are just the tip of the cosmic iceberg. These discoveries, made possible through years of dedicated collaboration and cutting-edge science, propel us on a journey to understand not only our celestial neighborhood but also the potential for life’s beginnings. With each revelation from Bennu, we draw closer to unraveling the mysteries of our cosmic heritage.”
Beyond science, these missions reflect the power of human curiosity and international teamwork, inspiring the next generation of explorers to push the boundaries of what we can achieve in space.
References:
- “NASA’s Bennu Asteroid Sample Contains Carbon, Water” – NASA.gov https://www.nasa.gov/news-release/nasas-bennu-asteroid-sample-contains-carbon-water/
- Barnes, J. J., Haenecour, P., … & Lauretta, D. S. (2024, March). Coordinated Analysis of Phosphates in Samples From Asteroid (101955) Bennu. In 55th Lunar and Planetary Science Conference (LPSC). Lunar and Planetary Institute.
- “Surprising Phosphate Finding in NASA’s OSIRIS-REx Asteroid Sample” – NASA.gov. https://www.nasa.gov/missions/osiris-rex/surprising-phosphate-finding-in-nasas-osiris-rex-asteroid-sample/
- Oba, Y., Koga, T., Takano, Y., Ogawa, N. O., Ohkouchi, N., Sasaki, K., … & Hayabusa2-initial-analysis SOM team. (2023). Uracil in the carbonaceous asteroid (162173) Ryugu. Nature Communications, 14(1), 1292.
- Lauretta, D. S., Connolly Jr, H. C., Aebersold, J. E., Alexander, C. M. O. D., Ballouz, R. L., Barnes, J. J., … & OSIRIS‐REx Sample Analysis Team. (2024). Asteroid (101955) Bennu in the laboratory: Properties of the sample collected by OSIRIS‐REx. Meteoritics & Planetary Science, 59(9), 2453-2486.
More by this author: The Power of Pacific— How ENSO is Shaping our World
Aly Muhammad Gajani holds a Master’s degree in Space Science and Technology, specializing in Astrophysics together with GIS applications. His research focuses on galaxy evolution, astrophysical cosmology, exoplanet detection, and computational astronomy.
