by On September 24, 2023, NASA’s OSIRIS-REx spacecraft dropped a capsule to Earth containing pristine carbonaceous regolith collected from the near-Earth asteroid Bennu. These samples were found after the probe made a remarkable seven-year journey through the solar system and back.
Since the arrival of these pieces of space rock (about 120 grams of a sample, to be precise) scientists are looking forward to an analysis of the specimens that can tell us what molecules are inside Bennu. They hoped to find clues about the history of our solar system, see how Bennu should have been present when our cosmic neighborhood was coming together, and prebiotic molecules that could shed light on the origin of life on the World. It is possible, according to many experts to speculate, that these samples could host the seeds of other essential ingredients, such as water, which could contribute to the habitability of the Earth if they also ended up on our planet.
“The sample we returned is currently the largest reservoir of unchanged asteroid material on Earth,” said Dante Lauretta, co-author of the paper and principal investigator of OSIRIS-REx at the University of Arizona, Tucson. in her. statement.
Although the initial studies did indeed show the OSIRIS-REx samples evidence of carbon and water on display, perhaps even more impressive than the team’s recent, and unexpected, discovery of magnesium-sodium phosphate. This is an ionic compound consisting of the magnesium cation (Mg2+) and the phosphate anion (PO43-).
Related: NASA’s OSIRIS-REx brings samples of asteroid Bennu to Earth after a historic journey of 4 billion miles
On Earth, sodium magnesium phosphate can be found in certain minerals and geological formations, as well as within living organisms where it is present in various biochemical processes and is a component of bone and teeth. However, according to a NASA press release, its presence on Bennu surprised the research team because it was not visible in the remote sensing data of the OSIRIS-REx probe before the collection of the samples. The team says its presence “suggests that the asteroid may have been splintered from a long-gone, tiny, primitive ocean world.”
“The presence and state of phosphates, as well as other elements and compounds on Bennu, suggest an aqueous past for the asteroid,” said Lauretta. “Bennu could once have been part of a wetter world. Although this hypothesis needs further investigation.”
The OSIRIS-REx spacecraft obtained a sample of Bennu’s regolith on October 20, 2020 using its Touch-and-Go Sample Acquisition Mechanism (TAGSAM), which includes a specialized sampler head mounted on an articulated arm. Bennu is a small B-type asteroid, which is a relatively rare carbonaceous asteroid. “[Bennu] They were chosen as the mission’s target in part because telescopic observations revealed a primitive, carbonaceous composition and water-bearing minerals,” the team said in their paper.
The sample was collected from a site called Nightingale, located in Hokioi Crater, an impact feature in Bennu’s northern hemisphere that is about 20 meters (66 feet) in diameter.
Further analysis of the samples revealed that the predominant component of the regolith sample is magnesium-bearing phyllosilites, mainly serpentine and smectite — rock types typically found at mid-ocean ridges on Earth. A comparison of these snakes with their terrestrial counterparts provides a possible insight into the geological history of Bennu. “To offer clues about the aquatic environment from which they came,” the team wrote.
Although Bennu’s surface may have been modified by water over time, it still preserves some of the ancient features that scientists believe were present during the early days of the solar system. Bennu’s surface materials still contain some basic elements from the cloud of gas and dust from which the planets of our solar system formed — known as the protoplanetary disk.
The team’s study also confirmed that the asteroid is rich in carbon, nitrogen and several organic compounds – all of which, along with magnesium phosphate, are essential components for life as we know it on Earth.
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“These results highlight the importance of collecting and studying material from asteroids like Bennu – especially low-density material that normally burns up upon entering Earth’s atmosphere,” said Lauretta. “This material holds the key to unraveling the complex processes of solar system formation and the prebiotic chemistry that may have contributed to the emergence of life on Earth.”
In addition to the important scientific discoveries made during this mission, it highlights the importance of the return of the samples to resolve the geological and geochemical complexity of asteroids like Bennu, and their implications for the formation and evolution of the solar systems.
“The data we have presented here is only the tip of the iceberg: there is probably more about the sample that we don’t know than we do,” the scientists said.
