Photoshop Question

Hey all! I have a random but important question. I’ve read the Greg Martin Tutorial on Planets and I’m really impressed by the results, but in this tutorials
http://www.good-tutorials.com/author/Art%20of%20Greg%20Martin
Is it possible to lets say layer a set texture as the planet base. IE, lets say I wanted to make Earth, how would I make the planet texture that way? Could I take a world atlas thing and “warp” it to the shape of the planet? Any ideas?