I really wanted to try and make a quick environment good as good as possible with as few resources as possible. At first I only used a 256x256 texture, but then I really felt I needed to add some unique features to the environment, so I added a planet, footprints and some normal map detail to the dunes. It still ended up smaller than a 512x512, so I'm very happy with that considering it's a large environment.
Impressive work. Been seeing a few of these exercises in modular textures pop up around the web, haven't tried something like that, but I really should.