[mkl]

Shadows in space are often very high contrast, as there's no ambient light. Simple 3D renderers don't handle ambient light either, as simulating it can be very computationally expensive (instead of e.g. one light source, pretty much everything in the scene acts as a light source with the light it reflects). These images in particular are also in near-infrared, so they may look a little different to colour images of Saturn you've seen.