Ceres' spots get curiouser as we get closer.
Probably ice (or maybe salt). But how did they form?
From http://www.nasa.gov/...
The region with the brightest spots is in a crater about 55 miles (90 kilometers) across. The spots consist of many individual bright points of differing sizes, with a central cluster. So far, scientists have found no obvious explanation for their observed locations or brightness levels.
"The bright spots in this configuration make Ceres unique from anything we've seen before in the solar system. The science team is working to understand their source. Reflection from ice is the leading candidate in my mind, but the team continues to consider alternate possibilities, such as salt. With closer views from the new orbit and multiple view angles, we soon will be better able to determine the nature of this enigmatic phenomenon," said Chris Russell, principal investigator for the Dawn mission based at the University of California, Los Angeles.
Meanwhile, another dwarf planet is showing a line.
http://www.planetary.org/...
New Horizons captured the four images used to make this view on June 6, 2015 from a distance of 46 million kilometers. Four images have been stacked and sharpened. The dark line running across Pluto is likely a real feature, not a processing artifact. Charon is still too small for any apparent features to be definitively discerned.
NASA / JHUAPL / SwRI / Björn Jónsson