What is a NormalMap texture ? On the contrary to its predecessor, the BumpMap, it indincate the elevation needed for a texture. In such way, you'll feel the montains height, you'll see the chasm profoundness, etc. This is an elaborate effect, very eye candy, it'll be hard to accept you don't have used it in Celestia before.

The use is pretty easy; you add the following row into a solarsys.ssc section (or in any alternate file) :

NormalMap "EarthNormal.dds"

That's all folk, the result is outstanding !