Nestled in the asteroid belt, the dwarf planet Ceres contains water-rich materials that suggest it once boasted a global ocean in its distant past. Now, two new studies from NASA's Dawn mission may reveal traces of an ancient ocean in the crust, with remnants left behind in the muddy mantle beneath. Scientists used the tug of gravity on NASA's Dawn spacecraft to track gravitational features across the dwarf planet Ceres. Combined with models of the evolution of the icy surfaces, these observations reveal an ocean mostly frozen into a strong but flexible crust, with a mud-rich inner layer that keeps...