Since the discovery by Piazzi, the asteroid Ceres remained totally unknown. Images taken from the ground did not reveal any surface detail. The HST space telescope succeeded to get an image with some details about the nature of the surface difficult to interpret. The presence of a bright spot was unusual for this type of object.
It's thanks to the probe Dawn who brought us images of unmatched precision that have been revealed the structure of the white spots on the surface. Water ice? salt deposits? It is difficult to answer but it seems that Ceres has a cometary activity.