Atmospheric Shader Help

Looking for an atmospheric shader I found some nice shaders, but the main problem is that the actually shaders creates a "halo" making this effect looks great from space, but the problem comes when I land into the planet. So I'm looking for a way to make a "3D" atmosphere, or a fade with the planet color (sky) to the space or vice versa. Maybe you've seen this effects in some games, like Spore.

I did it, just using a sphere with the normals inverted, the X-Ray shader and a flare texture. In Unity Free version.