Iapetus, Saturn’s third largest moon, is a total enigma. For a start, it’s a strange walnut shape. Secondly, it seems to have a surface purely rendered in black and white.
It looks a bit like snow on a mountaintop back here on Earth. Weirdly, in composition, it isn’t hugely different either. Iapetus is mostly made of ice. Only 20% of this little moon is rock. Those white patches are almost as shiny as Europa, making it quite likely that they’re patches of ice. The darker regions are thought to be from ice evaporating in the sunlight, leaving behind whatever else might have been trapped inside it. Once liberated from their icy prizon, these deposits of dark material are probably further blackened as they bake in the sun. It may not give much warmth anymore that far out in the solar system, but sunlight is still a driving force in a lot of things. Seemingly, it can even create sundried moons.
Image credit: NASA/JPL/Space Science Institute