I've been working on my technique for creating realistic Earthlike planets for a while. I figured I'd make a realistic picture of the Earth itself, but since my freehand drawing skill sucks when it comes to making continents, I went to the NASA website and downloaded a high-resolution cylindrical map of the Earth (in winter, as can be seen from the northern ice). From there, I manipulated the western part of the map into a sphere. The clouds and glow are purely my original creations. The Moon was also mapped from a NASA image, but I used an embossing filter to give it more texture. All done in Photoshop CS. Enjoy.