Ceres' spots not figured out yet

Even though there are even better images of them now, the composition of the bright white spots in Occator Crater on series has yet to be definitively determined.

This surprises me.  The white spots were the single greatest mystery that Ceres presented as the Dawn satellite probe approached.  They even started a contest in which people could guess what they were made of (I went with ice - mission scientists are now thinking salt of some kind).

And there were supposedly indications of an atmospheric trace in the crater, indicating that these patches might be subtly sublimating, also indicative of an icy nature.

But nothing has been stated yet.  It's starting to vex me.

Fresh views of Ceres but 'spots' remain mysterious  (with elevation and composition maps)