[yorwba]

They look like bad 3D renders because there are no walls and no sky in space, so all the light comes directly from the sun and shadows are absolutely black. The image looks different than with the naked eye though, because they filtered certain wavelengths. https://www.nasa.gov/jpl/cassini/pia18274

[est31]

The question is legitimate though as sometimes we do get 3D renders, e.g. when it comes to this image of the Korolev crater on Mars: https://www.esa.int/var/esa/storage/images/esa_multimedia/im...

They even added the fog (the fog in the picture is white and while there is dust on mars it's rather brown as the planet's surface https://mars.nasa.gov/imgs/mep/weather/PIA22520-600.jpg ).