nice, how did you make the atmosphere glow?
I made it this way, you can probably find a better or cheaper way since I'm no expert on this subject, anyways..
First of all make a new sphere a little bigger than the surface and put it on another layer, then:
1- Turn Fresnell to around 3, in the Mirror trans tab.
2- Turn Trashadow on, in the shaders tab, then play around with the colors your material will have, not sure if they are needed or not.
3- Turn on Traceable and Shadbuf if the are not already, in the Links and Pipeline tab.
4- Add a color ramp with the colors you want your atmosphere to have.
5- You'll have to use nodes to make the atmosphere look good, add the filters: Color-> RGB curve, Filter-> Blur and Color-> AlphaOver, connect the RGB curve to the atmosphere image, it will allow you to modify the color of the final render without having to render again, same with the blur, only that it will control the blurriness (?) of the sphere, and the alpha over is to combine the image with the terrain one, it takes the color black as alpha channel color if I'm not mistaken.
Take a look at the values, play around with them and you'll get what you need.
Oh remember to turn on composite on the Render layer, so you can use different render layers at the same time.
Here's an image of most of my settings in blender:
EDIT:
oh and since we are at it.. a little update
It's pretty much as far as I can get with my knowledge :s
Will add the background stars later this week.