Phosphate In NASA's OSIRIS-REx Asteroid Sample Suggests Ocean World Origins

Early analysis of the near-Earth asteroid Bennu has revealed unexpected evidence of magnesium-sodium phosphate, suggesting Bennu might have originated from a primitive ocean world. Space.com reports: On Earth, magnesium-sodium phosphate can be found in certain minerals and geological formations, as well as within living organisms where it is present in various biochemical processes and is a component of bone and teeth. According to a NASA press release, however, its presence on Bennu surprised the research team because it wasn't seen in the OSIRIS-REx probe's remote sensing data prior to sample collection. The team says its presence "hints that the asteroid could have splintered off from a long-gone, tiny, primitive ocean world." "The presence and state of phosphates, along with other elements and compounds on Bennu, suggest a watery past for the asteroid," said Lauretta. "Bennu potentially could have once been part of a wetter world. Although, this hypothesis requires further investigation." The OSIRIS-REx spacecraft obtained a sample of Bennu's regolith on October 20, 2020 using its Touch-and-Go Sample Acquisition Mechanism (TAGSAM), which comprises a specialized sampler head situated on an articulated arm. Bennu is a small B-type asteroid, which are relatively uncommon carbonaceous asteroids. "[Bennu] was selected as the mission target in part because telescopic observations indicated a primitive, carbonaceous composition and water-bearing minerals," stated the team in their paper. [...] Further analysis on the samples revealed the prevailing component of the regolith sample is magnesium-bearing phyllosilicates, primarily serpentine and smectite -- types of rock typically found at mid-ocean ridges on Earth. A comparison of these serpentinites with their terrestrial counterparts provides possible insights into Bennu's geological past. "Offering clues about the aqueous environment in which they originated," wrote the team. While Bennu's surface may have been altered by water over time, it still preserves some of the ancient characteristics scientists believe were present during the early solar system's days. Bennu's surface materials still contain some original features from the cloud of gas and dust from which our solar system's planets formed -- known as the protoplanetary disk. The team's study also confirmed the asteroid is rich in carbon, nitrogen and some organic compounds -- all of which, in addition to the magnesium phosphate, are essential components for life as we know it on Earth.

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