06-05-2015, 10:16 AM
Comets have a high percentage of ice in their composition. Maybe its the remains of a comet impact. Also, Pluto and Ceres are way out at the outer edge of our solar system. They are at, or very close to a region called the Kiuper Belt which is part of the Oort Cloud where many comets are thought to originate. It follows that there may be many other smaller icy bodies out there....one of which may have collided with Ceres.
