For months, the bright spots on the surface of Ceres captured by the Dawn spacecraft's cameras have stumped NASA's scientists. Now, thanks to a study led by Andreas Nathues from Germany's Max Planck Institute for Solar System Research, they can finally say that those spots are most likely not volcanic formations. The team has identified the shiny material inside the dwarf planet's craters as hexahydrite: one form of magnesium sulfate. Since that compound is an inorganic salt, you can say that those craters glow due to their salt deposits. You know what else is magnesium sulfate, by the way? Epsom salts -- though it's a different type altogether.