Re: geological question
On Earth, satellite photos have value. Individual ERS and Landsat frames sell for a few hundreds or thousands of dollars. Spy satellite photos are highly sought after.
Some images are available from Shuttle flights, but the Shuttle SAR dataset has been squirreled away for commercial sale.
One interesting cache of images is Terraserver, but they screw with your computer and stop you saving the images. However, there are some interesting pics, including the US nuclear test sites in Nevada and the notorious "Area 51"
http://www.terraserver.com/