A tiny fraction of the asteroid Bennu sample returned by NASA’s OSIRIS-REx mission, shown in microscope images. The top-left pane shows a dark Bennu particle, about a millimeter long, with an outer crust of bright phosphateOn September 24, 2023, NASA's OSIRIS-REx spacecraft dropped a capsule to Earth containing pristine carbonaceous regolith collected from the near-Earth asteroid Bennu.
"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.
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.