What are the bright spots on Ceres?

An odd anomaly is happening on one of our dwarf planets.:The dwarf planet Ceres (as seen by the Dawn spacecraft) is giving scientists a headache...

From National Geographic's "Are We Alone?" special magazine:
What are the bright spots on Ceres?

Ceres is the largest object in the asteroid belt that lies between Mars and Jupiter. Ceres's size and round shape earned it the classification of dwarf planet in 2006. Early in 2015 NASA's Dawn spacecraft approached Ceres and produced striking photos of its surface, revealing a pair of mysterious bright spots nestled in a crater (right). The spots appear to vary in brightness as the dwarf planet rotates, and they remain visible as that area of Ceres moves out of view. That means they are affected by sunlight and are tall enough to be seen over the crater wall.

Scientists are still investigating this odd anomaly. The prevailing hypothesis is that because Ceres almost certainly has a great deal of ice, we may be peering from a distance at a so-called cryovolcano—not unlike an earthly volcano but far colder, erupting water and methane instead of lava. As bizarre as that sounds, cryovolcanoes are believed to be fairly common in the colder parts of the solar system, from Neptune's moon Triton to Jupiter's moons Europa and Ganymede, to Saturn's Titan.


From National Geographic's "Are We Alone?" special magazine: