Ceres has long been a mystery to scientists. It has been speculated that Ceres may have a water-vapor plume. The Herschel Space Observatory spotted water vapor coming from two locations. It is speculated that it could be caused by icy volcanoes.
The bright spots were speculated to be water-ice or some other form of ice (such as frozen carbon dioxide, AKA dry ice). Another theory is that this portion of Ceres has a rock-like feature that reflects light differently than the rest of Ceres.