When most folks imagine the asteroids, they likely picture chunk of rocky rubble, maybe mixed in with some metals based on distant observations and flybys. They shouldn't be very complicated because they're just leftovers from the formation of the solar system. Most of the meteorites that have been sampled on Earth have a lot of the same basic minerals and elements as well.
As it turns out, going out to the asteroid belt and directly sampling one of these primordial objects has turned that notion around. The pristine sample of Bennu, visited by OSIRIS-REx in 2023, is absolutely full of minerals that weren't expected. And those minerals seem to suggest that Bennu -- or more likely whatever its progenitor object was -- may have been a lot wetter than we might have guessed.
