Scientists have made an exciting discovery about the near-Earth asteroid Bennu: it contains the original ingredients that formed our solar system.
The findings come from a sample of rocks and dust brought back by NASA’s OSIRIS-REx mission, revealing surprising details about the asteroid’s composition.
Bennu’s dust is rich in carbon and nitrogen, essential elements for life. The sample also contains a surprising find: magnesium sodium phosphate, which wasn’t detected by the spacecraft’s remote sensors.
This suggests Bennu might have once been part of a small, primitive ocean world that no longer exists.
The OSIRIS-REx spacecraft, launched on September 8, 2016, traveled to Bennu to collect samples from its surface.
This was the first US mission to do so. The spacecraft returned to Earth on September 24, 2023, carrying 4.3 ounces (121.6 grams) of Bennu’s rocks and dust.
“Finally being able to study the OSIRIS-REx sample from Bennu after all these years is incredibly exciting,” says Dante Lauretta, the mission’s principal investigator and a professor at the University of Arizona.
“This discovery not only answers long-standing questions about the early solar system but also opens new research paths into how Earth became habitable.”
Lauretta co-authored a paper in the journal Meteoritics & Planetary Science, detailing the nature of the Bennu sample.
This paper also introduces the Bennu sample catalog, an online resource where scientists can request sample material for their own studies.
A Watery Past?
The analysis of Bennu’s sample revealed intriguing details about its composition. The sample is dominated by clay minerals, especially serpentine, similar to rocks found at mid-ocean ridges on Earth.
These ridges are where the Earth’s mantle, the layer beneath the crust, meets ocean water, creating various minerals, including carbonates, iron oxides, and iron sulfides.
The most unexpected discovery in Bennu’s sample was water-soluble phosphates, essential for all known life on Earth. These phosphates suggest Bennu may have once had interactions with water, indicating a possible wet past.
A similar phosphate was found in the asteroid Ryugu sample, brought back by the Japan Aerospace Exploration Agency’s Hayabusa2 mission in 2020. However, the magnesium sodium phosphate in Bennu’s sample is unique due to its lack of inclusions and large grain size, unlike any meteorite sample seen before.
This discovery raises questions about the geochemical processes that formed these elements and provides valuable clues about Bennu’s history.
“The presence and state of phosphates on Bennu suggest it might have once been part of a wetter world, although further investigation is needed,” Lauretta explains.
Despite its potential watery past, Bennu remains a chemically primitive asteroid, with elemental proportions similar to those of the sun. The rocks and dust from Bennu have stayed in their original state for over 4.5 billion years, providing a glimpse into the early solar system.
The team also confirmed that Bennu is rich in carbon and nitrogen, crucial for understanding the environments from which Bennu’s materials originated. These findings help scientists explore the chemical processes that transformed simple elements into complex molecules, possibly setting the stage for life on Earth.
“These findings highlight the importance of collecting and studying material from asteroids like Bennu, especially low-density material that would usually burn up in Earth’s atmosphere,” Lauretta says. “This material holds the key to understanding the solar system’s formation and the prebiotic chemistry that could have led to life on Earth.”
In the coming months, dozens of labs in the United States and worldwide will receive portions of the Bennu sample for further analysis. Many more scientific papers are expected from the OSIRIS-REx Sample Analysis Team, providing new insights into the origins and evolution of planets like Earth.
“Each week, our analysis team finds new and sometimes surprising results, helping us understand how Earth-like planets formed and evolved,” says Harold Connolly, co-lead author of the paper and mission sample scientist.
Source: University of Arizona.
