The researchers found traces of carbon, nitrogen, organic compounds, sodium phosphate and magnesium in the sample. This is an unexpected mineral that suggests a possible watery past for Bennu.

On September 24, 2023, the OSIRIS-REx spacecraft returned to Earth after visiting the asteroid Bennu. During this visit, the probe collected dust and pebbles that arrived on Earth on that unforgettable day. Since then, scientists have studied the samples extensively. Now they are sharing their first amazing discoveries.

About Pino
Bennu is an extremely ancient asteroid, dating back to the earliest days of our solar system, and its composition has remained largely unchanged since then. This asteroid, or the material it is made of, is expected to give us insight into the conditions under which planets like those in our solar system formed. Asteroids are actually remnants from the early period of our solar system, like time capsules that help us study the origins of our solar system. But that’s not all. Bennu may also play a crucial role in understanding the origins of life on Earth. Asteroids are thought to have delivered important building blocks for life, such as organic matter and water, to planets like Earth through collisions. In this way, they may have made a fundamental contribution to the origin of life, including our own existence. By studying Bennu’s organic molecules, we can better understand what kinds of molecules asteroids may have delivered to the young Earth.

Scientists have been eagerly awaiting the opportunity to examine the original 121.6-gram Bennu sample collected by NASA’s OSIRIS-REx mission since it was returned to Earth last fall. They hoped the material would reveal secrets about our solar system’s past and the biochemistry that may have helped give rise to life on Earth. Early analysis of Bennu’s sample reveals this.

complex
Analysis of the Bennu sample has provided very interesting insights into the asteroid’s composition. The sample turned out to contain carbon, nitrogen and organic compounds, all essential components of life as we know it. These elements are essential to understanding the environments in which Bennu’s materials formed and the chemical processes that transformed simple elements into complex molecules, which may have laid the foundation for the emergence of life on Earth. “These discoveries highlight the importance of collecting and studying material from asteroids like Bennu,” emphasizes Dante Lauretta, co-author and principal investigator of OSIRIS-REx. “Light-weight materials in particular, which typically burn up upon entering Earth’s atmosphere, provide valuable insights. This material is essential for understanding the complex processes that led to the formation of our solar system and the chemical steps that may have contributed to the origin of life on Earth.”

serpentine
In addition, the sample consists mainly of clay minerals, especially serpentine, and is very similar to the type of rock found in mid-ocean ridges on Earth, where material from the mantle, the layer beneath the Earth’s crust, comes into contact with water. This reaction leads to the formation not only of clay, but also of a variety of minerals such as carbonates, iron oxides and iron sulfides.

Sodium magnesium phosphate
But the biggest surprise was the discovery that the sample contained water-soluble phosphate, specifically sodium magnesium phosphate. This metal was a surprise because the OSIRIS-REx spacecraft did not detect it while on Bennu. Water-soluble phosphate is essential to the biochemistry of all known life forms on Earth. Although similar phosphate was found in the Ryugu sample returned by the Japan Aerospace Exploration Agency’s Hayabusa 2 mission in 2020, the sodium magnesium phosphate in the Bennu sample is distinguished by its exceptional purity – that is, the absence of other substances in the mineral – and unprecedentedly large quantity. Grain size, something that has never been observed before in a meteorite sample.

What does this mean?
The discovery of sodium and magnesium phosphate in Bennu’s sample raises questions about how these elements are concentrated by geochemical processes. This provides important clues about the conditions that prevailed in Bennu’s past. The presence of sodium and magnesium phosphate in Bennu’s sample indicates that the asteroid may have come from an ancient, young, primitive world with oceans. Loretta believes that “the presence of phosphate, along with other elements and compounds on Bennu, indicates that the asteroid had a watery past.” “It is possible that Bennu was part of a wetter world in the past, although this hypothesis requires further research.”

Young solar system
Despite possible interactions with water in the past, Bennu remains a chemically primitive asteroid, with element ratios very similar to those of the Sun. “We now have the largest collection of unaltered material from an asteroid on Earth,” Loretta said. This formation gives us a glimpse into the early days of our solar system, more than 4.5 billion years ago. These rocks have not melted or solidified again since their formation, which confirms that they have retained their original state and are therefore very old.

What now?
This first analysis is just the tip of the iceberg. Dozens of other laboratories will receive portions of the Bennu sample in the coming months, which will likely lead to many scientific papers detailing Bennu sample analyzes in the coming years. “Bennu’s samples are beautiful, exciting pieces of exotic rock,” said Harold Connolly, co-author and OSIRIS-REx mission scientist. “Every week, the OSIRIS-REx sample analysis team makes new and sometimes surprising discoveries, providing important insights into the origin and evolution of planets like Earth.”

But this is not the case yet. The current study was published in the journal Meteorites and planetary science, is indeed a great first step in explaining the Bennu monsters. The analysis not only increased our knowledge of asteroids, but also provided valuable insights into the building blocks of life and the dynamic processes that influenced the formation of our solar system. “OSIRIS-REx has given us exactly what we hoped for: a large, authentic sample of a nitrogen- and carbon-rich asteroid from a former water-rich world,” concludes OSIRIS-REx project scientist Jason Dworkin.