Originally Posted by Joe Obenberger

Let me give it a try.

1. It's not only there. When any comet comes close enough to the sun, it lights up brilliantly reflecting sunlight, sometimes so much of it that the brightest comets become visible in the daytime sky here. Satellite and astronaut photos show how brightly polar ice and clouds reflect that light, and many of the same photos show strong reflections from the sun on the oceans and other surface water. All of what we can see of other planets and natural satellites comes from reflected sunlight.

2. Mars has thin polar caps. They come and go in intensity because of climate and we don't think they are very exceptional because our home planet has similar polar caps.

3. I think what you're asking is why, if this is ice, there are only two spots of it and because they near the equator of Ceres, far away from the presumably colder poles. We have not seen that anywhere else. Let me venture a guess. We've recently learned that Mars is likely to have broad expanses of ice, frozen ground that would be like a marsh if the temperature were warmer. The scientists think that it's covered by a thin layer of soil where the ice exists. And if this ice were not covered by Mars soil, maybe it would reflect, too. Maybe Ceres has a similar structure, with frozen marshy soil, ice together with dirt, and covered by a thin layer of dirt. One possibility is that the topsoil got removed by a meteor strike. Another possibility is that the ice lies at the bottom of a steep crater, and that it does not melt because it is so far from the sun. The most interesting possibility is that it's caused by a massive outcropping of shiny metal or crystal - and maybe, too, a meteor strike uncovered these two spots by removing the soil.