I used 5 textures: One for surface color, one for surface bump, then a specular map for the suraface that i pluged to specular roll off of the blin material that i used for the surface.Then for the clouds sphere, i used a color map with alpha channel for transparency, ans also a bump map for clouds , that is derived from the clouds map (you know ...desaturate then levels in photoshop).This is a sample of the clouds map(640X320). PS: all maps have 8K.