The best photo yet of those mysterious bright spots on dwarf planet Ceres as captured by the Dawn space probe just 4,500 kilometers above the pock-marked surface of this just-barely-spherical world-let.
Ceres is the largest asteroid -- and a dwarf planet -- in the Solar System's Asteroid Belt with a mean radius of approximately 476 kilometers, an equatorial radius of just a touch over 487 kilometers, and a polar radius of just under 455 kilometers. All three of these figures are estimates with error bars of about 2 kilometers.
This is a close-up of the spots taken by Dawn on May 4, 2015. The probe was about twice as far away (8,500 miles) from Ceres than in the lead image, but this is zoomed-in close-up.
There is a real complexity to the shapes of these bright spots.
What exactly are these spots? Possibly reflective water ice, possibly salt, some other physical phenomenon, or just possibly the lights of some alien civilization's beacon (OK, that last one is rather unlikely). At the end of the day, they still remain a mystery.
NASA offers you the chance TO VOTE on what you think those bright spots are! The assumption is that it is some material reflecting sunlight, but the cause is one of six possibilities: a volcano, geyser, rock, water ice, salt deposit, or an unspecified something else.
Whatever they are, as the late, great Leonard Nimoy's Spock would have said, "Fascinating ..."