NASA has uploaded 3D printable designs to their website in STL format. The new 3D printable library currently includes 21 different objects in STL format. They include asteroids, moon surfaces, mars surfaces and craters, space craft and more. Several of the available files don't appear to be prepared very well for 3D printing due to their small detailed pieces. Other objects have been cut in half by NASA to make them easier to print. Read more about this, and see some photos at http://3dprint.com/10099/nasa-3d-printable-models/