'tis the Seasoning: Bright Spots on Ceres Are Very Probably Salt

The Dawn spacecraft has been orbiting the protoplanet* Ceres in the main asteroid belt since March 2015, sending tremendous amounts of data back to astronomers on Earth. Ceres is an odd beast, the biggest object in the main asteroid belt between Mars and Jupiter. It's very dark, and known be mostly rock but with a substantial amount of water ice under the surface. It has no atmosphere to speak of. That much was known before Dawn got there. But as it arrived, pictures it sent back revealed a surp...