In case people haven't seen these before:
http://antwrp.gsfc.nasa.gov/apod/ (http://antwrp.gsfc.nasa.gov/apod/)
This photo gave me a completely new look on what Mars looks like. Very interesting.
I think this is something that would be a good Terragen exercise for me to build someday when I have mastered the terrain techniques ;D
https://isis.astrogeology.usgs.gov/IsisSupport/index.php?topic=1166.0