It must be the clouds because there is no surfacing in this image beyond the brown base color fractal with a very large average scale. As to getting a grain from high altitudes, it has a lot to do with the fractal roughness, contrast, noise variation, buoyancy of variation, noise octaves, and scales. The color of the surface is also important (i.e. how much does the color stand out from the other colors). Perhaps I will try to make some kind of tutorial about it soon.
Besides making a bunch of renders and trying to make them better, I don't know what I'm going to do with my planet stuff. I'm no expert. I think the big push behind all of it has always been to create a complete planet -- from meters up to thousands of kilometers in space (a goal I have yet to accomplish). If anything, I might just make some tutorials sometime.
