On September 24, 2023, NASA’s OSIRIS-REx spacecraft delivered a capsule with carbon regolith to Earth, collected from the near-Earth asteroid Bennu. The samples were obtained after the probe made a seven-year journey through the solar system.
«The sample we returned is the largest reservoir of unaltered asteroid material on Earth at this time», — wrote Dante Lauretta, one of the lead authors of the paper and principal investigator of OSIRIS-REx from the University of Arizona.
Initial research has shown that OSIRIS-REx samples show evidence of carbon and water. They also unexpectedly found magnesium and sodium phosphate. This is an ionic compound consisting of magnesium cation (Mg2+), sodium cation (Na⁺), and phosphate anion (PO43-).
On Earth, magnesium and sodium phosphate can be found in some minerals and geological formations. Its presence on Bennu surprised the research team, as the substance was not seen in the OSIRIS-REx remote sensing data before the sample collection began. The team says its presence «hints that the asteroid may have broken away from a long-vanished, tiny, primitive ocean world».
«The presence and condition of phosphates, as well as other elements and compounds on Bennu, indicate a watery past for the asteroid. Bennu could potentially have once been part of a wetter world. Although this hypothesis needs further investigation,» Lauretta said.
OSIRIS-REx obtained a sample of Bennu’s regolith on October 20, 2020, using the Touch-and-Go Sample Assembly Mechanism (TAGSAM), which consists of a special sampler head mounted on an articulated arm. Bennu is a small B-type asteroid, which is a relatively rare carbonaceous asteroid.
«[Bennu] was chosen as the mission target in part because telescopic observations indicated a primitive, carbonaceous composition and water-bearing minerals», — the study publication says.
Further analysis of the samples showed that the predominant component of the regolith sample is magnesium-bearing phyllosilicates, mainly serpentinites and smectites — rock types commonly found on mid-oceanic ridges on Earth. Comparison of these serpentinites with their terrestrial counterparts provides a possible insight into Bennu’s geologic past. At the same time, the asteroid’s surface materials still contain some of the original features of the protoplanetary disk from which the planets of the Solar System were formed. The study also confirmed that Bennu is rich in carbon, nitrogen, and some organic compounds — all of which, except magnesium phosphate, are important components for life on Earth.
An article about these results was published on June 26 in the journal Meteoritics & Planetary Science.
Source: Space.com