First, we have Saturn imaged through the infrared (redder than red) that brings out details that the human eye cannot detect. Note the gossamer rings, and their dark shadow. Note also the contrast between the bright (and warmer) south, just now coming to the end of a seven-year summer and the cooler north emerging from a long winter under the shadow of the rings.
Mercury looks a lot like the moon at first glance, but there are subtle differences. Mercury lacks maria (Latin for seas) those dark lava plains which define the face of the “man in the moon.” Mercury’s rugged terrain is generally darker than the moon’s. More ridges and wrinkles on Mercury, too.
Two solar system icy moons, Ganymede and Titan, are bigger, but Mercury masses more because of a metal core and a high density.