Blender 2.75: Create a Realistic Earth
In this tutorial you will discover how to model, texture and composite a realistic earth in blender, using Cycles.
The following link guides you to a NASA map collection. There you'll find The cloud-, bump- and colormap, as well as the city lights texture. For a realistic look pick one of those colormaps that don't have topography nor bathymetry:
http://visibleearth.nasa.gov/view_cat...
You will find the spec-map here:
http://qgv6y6drlr2sy3es4blouyvd9.wpen...,
but it will probably not suit well in the northpole region, depending on the colormap you chose. It's better to create a custom one deriving from your colormap, using gimp. Select all blue color and bucket-fill it black. Inverse the selection and fill it white. Done.
And be careful: some of that NASA pictures are quite big. Scale them down in gimp if needed.