In one of the most anticipated moments in space exploration, NASA’s OSIRIS-REx space probe made its dramatic return to Earth after a two-year journey from asteroid Bennu, delivering a small capsule containing a sample of the asteroid’s surface material. On September 24, 2023, the capsule, weighing just 122 grams of dust and rock, was successfully recovered in the desert of Utah, USA. This moment marked the culmination of a groundbreaking mission that will provide crucial insights into the early solar system and the building blocks of life on Earth.
The Journey and the Touch-and-Go Maneuver
OSIRIS-REx, short for Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer, was launched in 2016 with the primary goal of collecting samples from the near-Earth asteroid Bennu. Bennu, a 500-meter-wide asteroid composed of loose, unconsolidated material, was chosen for its potential to hold ancient material from the early solar system. Scientists believe that by studying these samples, they could gain a deeper understanding of the processes that led to the formation of planets and the development of life.
In October 2020, after years of orbiting and studying the asteroid, OSIRIS-REx performed a touch-and-go maneuver—affectionately known as TAG—to collect a sample from the surface of Bennu. The maneuver was incredibly delicate, requiring the spacecraft to make brief contact with the asteroid’s surface for just a few seconds. The spacecraft’s robotic arm extended to gather regolith, the loose dust and rock, before quickly retreating to avoid contamination or loss of the precious sample.
The sample collection was remarkably successful, and despite initial concerns about the amount of material collected, the spacecraft gathered more than enough dust and rock to meet its mission goals. In May 2021, OSIRIS-REx began its return journey to Earth, taking two years to cover the vast distance before finally releasing the sample capsule on September 24, 2023.
Sample Analysis: A Global Effort
The contents of the sample—dust and rock from a body that has not been significantly altered for over 4.5 billion years—offer a unique opportunity for scientists to study the origins of our solar system. Once the capsule safely landed in Utah, the precious cargo was transported to NASA’s Johnson Space Center in Houston, Texas, for preliminary analysis. But the real work began when scientists from over 40 institutions worldwide, including a team from Goethe University Frankfurt in Germany, began their detailed investigations.
The team of geoscientists from Germany, led by Dr. Sheri Singerling, Dr. Beverley Tkalcec, and Prof. Frank Brenker, used state-of-the-art technology to analyze the samples. They focused on studying the mineral grains from the Bennu sample, using the transmission electron microscope at the newly established Schwiete Cosmochemistry Laboratory in Frankfurt. The lab was set up just a year before the sample’s arrival to provide cutting-edge tools for this complex analysis.
The key objective of the German team was to uncover the processes that took place on Bennu’s protoplanetary parent body—the larger celestial body from which Bennu originated—more than four billion years ago. These processes ultimately contributed to the formation of the minerals that exist on Bennu today.
By examining the grains’ mineralogical structure and chemical composition, the scientists were able to reconstruct the conditions under which these minerals formed. This study revealed that the surface of Bennu—and by extension, its parent body—experienced conditions conducive to the formation of evaporite minerals, a class of minerals that form when salty water (or brine) evaporates. The evaporites formed as minerals precipitated in order of their solubility, much like the salt deposits left behind in dried-out salt lakes on Earth.
This discovery suggests that Bennu’s parent body may have had liquid water—potentially for extended periods—creating a favorable environment for the formation of complex chemistry. In fact, some of the minerals identified were directly related to the kinds of organic molecules that are key to life as we know it, such as amino acids and precursors to biomolecules.
A Glimpse into the Ancient Solar System
The findings from the analysis of Bennu’s surface materials reveal that the asteroid’s parent body underwent significant processes in its early history, potentially involving liquid water. These processes took place over four billion years ago, before the parent body broke apart to form Bennu, preserving the ancient chemical record within the asteroid’s surface material. However, due to the break-up of the parent body, these processes were interrupted early on, and the chemical traces preserved in the sample have remained largely unchanged for over 4.5 billion years.
The presence of these organic building blocks and evidence of past liquid water raise intriguing possibilities about the potential for life elsewhere in the universe. Prof. Frank Brenker, one of the leading scientists on the project, suggests that other celestial bodies, such as Saturn’s moon Enceladus and the dwarf planet Ceres, may have undergone similar processes. Both of these bodies are believed to harbor subsurface oceans or traces of liquid water beneath their icy exteriors, making them prime candidates for future exploration in the search for life.
“Since these bodies may have had liquid water and the necessary building blocks for life, they could have supported simple life forms in the past—or may still have the potential to do so today,” says Brenker. The discovery of organic molecules and evaporites on Bennu suggests that these celestial bodies could be harboring the ingredients for life, making them key targets for future space missions.
Implications for Future Space Exploration
The work done by the team from Goethe University and their international collaborators is a significant milestone in our understanding of the early solar system and the potential for life beyond Earth. The discovery of organic compounds, evaporites, and the history of liquid water on Bennu’s parent body provides crucial clues about the processes that led to the formation of life on Earth.
In addition to this, the study of Bennu’s sample serves as a stepping stone for future space exploration. Understanding the mineralogy and chemistry of asteroids like Bennu allows scientists to develop more accurate models of how planets and other celestial bodies formed in the early solar system. This knowledge will also guide future missions to other asteroids and moons, such as those of Jupiter and Saturn, in the search for signs of life or prebiotic chemistry.
The OSIRIS-REx mission has also set the stage for future sample-return missions, not just to asteroids, but potentially to comets and other small bodies in the solar system. These missions will help us understand not only the origins of the solar system but also the broader questions of how life might have arisen on Earth and whether life could exist on other planets and moons.
As scientists continue to analyze the Bennu samples, we can expect even more insights into the nature of the early solar system, the potential for life beyond Earth, and the conditions that may have made Earth a cradle for life. The OSIRIS-REx mission and its international partners are making history by unlocking the secrets of the solar system’s past—and perhaps offering clues to the future of life in our universe.
Conclusion
The return of the OSIRIS-REx mission’s sample from asteroid Bennu has provided the scientific community with a rare and valuable glimpse into the early history of our solar system. By examining the dust and rock collected from the asteroid’s surface, scientists are piecing together a picture of the conditions that prevailed on Bennu’s protoplanetary parent body billions of years ago. This research not only deepens our understanding of how the solar system formed but also raises the exciting possibility that the building blocks of life—water, organic molecules, and the right chemical conditions—were once widespread in the cosmos. As we continue to study Bennu’s ancient sample, the quest for knowledge about the origins of life and the potential for life elsewhere in the universe is moving forward.
Reference: Tim J. McCoy et al.: An evaporite sequence from ancient brine recorded in Bennu samples. Nature (2025). DOI: 10.1038/s41586-024-08495-6, www.nature.com/articles/s41586-024-08495-6