The Asteroid Bennu Has Just Revealed a Clue About the World It Came From. The Key Is in Its Phosphates

Studying Bennu may offer clues about the origin of life on Earth. For now, it has revealed one about its own.

Asteroid Bennu’s phosphates has just revealed a clue of the world it came from
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Pablo Martínez-Juarez

OSIRIS-REx is one of the most ambitious space missions in recent years. The spacecraft traveled to the asteroid Bennu, collected samples from its surface, and brought them back to Earth. Mission managers have been analyzing the samples since September.

A new clue. This analysis revealed a new clue about Bennu’s origin, found in the sample’s phosphate, indicating that this space rock came from an “oceanic world.”

121.6 grams. The study is based on one of the first sample analyses brought back to Earth by the OSIRIS-REx mission: 121.6 grams of rock and dust from Bennu.

But this isn’t the first analysis of this material. Previous studies indicated the presence of dust rich in carbon, nitrogen, and organic compounds. NASA explains that these are essential components of life as we know it.

They also indicated the presence of clay minerals such as serpentine. This material is similar to that found on our planet in mid-oceanic ridges, which suggests submerged land.

Magnesium-sodium phosphate. The discovery of these materials was just what NASA expected. The space agency chose Bennu because it’s an asteroid formed during the first millions of years of the solar system. NASA wanted to study these primordial materials to know “the secrets of the solar system’s past and the prebiotic chemistry that could have led to the origin of life on Earth.”

However, the team was surprised to discover magnesium-sodium phosphates. The remote sensing systems of the OSIRIS-REx spacecraft hadn’t detected any traces of these compounds.

Ocean world? According to the agency, this type of material suggests that Bennu may have originated in an aquatic world. This hypothetical body could have been an “ancient, small, [and] primitive oceanic world.”

The team explains in a press release that confirmation of this hypothesis will require further study of the material. “Bennu potentially could have once been part of a wetter world. Although, this hypothesis requires further investigation,” Dante Lauretta, one of the study's co-authors, said.

Researchers detailed the new analysis in a paper published in Meteoritics & Planetary Science.

A seven-year journey. The OSIRIS-REx mission set out to meet Bennu in September 2016. In October 2020, the NASA mission tore off a piece of the asteroid’s surface regolith with its robotic arm, which is equipped with the Touch-and-Go Sample Acquisition Mechanism (TAGSAM).

In late September 2023, just over seven years into the mission, a capsule landed in the Utah desert with the most significant unadulterated asteroid sample ever collected. The fact that the sample was pristine is vital: Many asteroids reach Earth as meteorites, but they’re affected by the conditions of entry and arrival to our planet.

While heat and water affect their chemical composition, but because the sample was protected by a capsule, it got here in its most intact form. “These findings underscore the importance of collecting and studying material from asteroids like Bennu—especially low-density material that would typically burn up upon entering Earth’s atmosphere,” Lauretta added.

Image | Lauretta, Connolly, et al., 2024

Related | NASA’s Perseverance Rover Hasn’t Just Collected Rocks on Mars: Its Tubes Contain Another Valuable Sample

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