Asteroid Bennu was part of an ancient ocean world

Since the arrival of a sample of asteroid Bennu on Earth in September 2023, delivered by NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer) spacecraft, expectations have continued to grow for the results of the long-term study and the thorough initial analysis to which the sample was subjected.

The material was expected to hold secrets about the solar system’s past and the prebiotic chemistry that may have led to the origin of life on Earth. And this first analysis of Bennu’s sample shows that hope has been realized.

The team, which includes, among others, Dante Lauretta from the University of Arizona in Tucson, US, and a member of the OSIRIS-REx science team, discovered that Bennu contains the original ingredients from which the Earth and other stars were formed. Our Solar System. Asteroid dust is rich in carbon and nitrogen, as well as organic compounds—all essential components of life as we know it. The sample also contains sodium magnesium phosphate. Its presence in the sample suggests that it is likely that the asteroid was part of an ocean world in the distant past. Probably due to a collision with a massive star, that primordial world with the potential for life was destroyed, and one of its pieces is Bennu today.

The sample, which is dominated by clay minerals, especially serpentine, has much in common with the type of rock found in Earth’s ocean ridges, where mantle material, the layer of water beneath the Earth’s crust, is found.

This interaction leads not only to the formation of clays, but also various minerals such as carbonates, iron oxides and iron sulfides.

But the most surprising discovery in the Bennu sample is the presence of water-soluble phosphates. These substances are components of the biochemistry of all life currently known on Earth.

A particle approximately 1 millimeter long from a sample taken by OSIRIS-REx from the asteroid Bennu. (Photo: Lauretta & Connolly et al. (2024) Meteoritics & Planetary Science, doi:10.1111/maps.14227)

In the coming months, NASA’s Johnson Space Center will deliver portions of the Bennu sample to dozens of labs inside and outside the U.S., and it’s likely that all of these future analyses will provide relevant information.

The OSIRIS-REx space probe left Earth in 2016 and arrived at the asteroid Bennu in 2018. After an extensive series of observations, including a brief descent to the surface to collect soil samples, the spacecraft began its return journey on May 10, 2021. to the ground. On September 24, 2023, OSIRIS-REx released a capsule containing samples of Bennu when it was 102,000 kilometers from the Earth’s surface (about one-third of the distance between the Moon and Earth). The capsule completed the rest of its journey to Earth on its own.

When OSIRIS-REx completed its mission to explore Bennu, its scientific instruments were still in perfect condition and it still had a quarter of its fuel remaining. So instead of shutting down the ship after delivering the sample to Earth, it was decided to send it on a follow-up mission to another asteroid: Apophis. As a result of the new mission, the ship’s name was changed, and it has since become OSIRIS-APEX (Origins, Spectral Interpretation, Resource Identification, and Security – Apophis Explorer).

As part of the orbital maneuvers around the Sun that the spacecraft must make to eventually rendezvous with Apophis, it came within 75 million kilometers of the Sun a few months ago, much closer than the distance between Venus and the Sun (108 million kilometers). Surviving the heat of this region of the Solar System is quite a feat for this spacecraft, considering that it was not designed to get so close to our star or to carry out the mission it is currently on. (Fountain: NCYT by Amazings)