Join planetary scientists Beth Johnson and Ian Pamerleau, lead author of a groundbreaking new Nature Astronomy study, for a deep dive into the icy mysteries of Ceres—the largest object in the asteroid belt and the only dwarf planet to be orbited by a spacecraft. While Ceres shows signs of an ice-rich interior, its heavily cratered surface doesn’t behave like soft, ice-laden terrain. So what gives? To solve the puzzle, Pamerleau and colleagues used simulations and an updated model of how impure ice deforms. Their work reveals that Ceres once hosted a subsurface ocean that froze from the top down, concentrating impurities as it solidified and creating a gradient from ice-rich surface layers to a rockier interior. (Recorded live 10 July 2025.)