Had some Mars pattern digital camouflage and was looking for a project to work with it on. MARSFOR, or Mars Force represents a fictional security force based in a future Mars colony. The astronauts are from the SketchUp 3D Warehouse, in particular, the "MAX GRÜTER" collection.
The background image is taken from a NASA Mars rover panorama. The dirt texture was just changed in GIMP from typical Earth-bound colors to a red more suitable for Mars.
The concept behind these armored transports are to have them large enough to sustain their crew for long periods "in the field." On earth, most down time would be spent outside the vehicle, however on Mars this is not practical, so the larger interior is meant to compensate for this and provide round-the-clock shelter. The long range guns and heavy machine guns on the front are meant to engage targets in the open and the large wheels meant to allow the vehicles to move quickly over rough terrain.
