The asteroid Bennu is the fragment of an ancient ocean planet - Space and Astronomy. The phosphate crust that covers the Bennu samples is something never seen before in meteorites.
Such high concentrations of phosphate have been detected on oceanic planets. For example, Saturn's moon Enceladus contains phosphate, a key element for life that is found in quantities significantly higher than those present in Earth's oceans. "It's still highly speculative, but at the moment it's the best lead I have to explain the origin of that material," concludes Dante Lauretta.