An awesome planetary rendering engine which in my opninion would suit the ED game perfectly is
Outerra Anteworld.
This light-weight engine can easily render entire planets, from space to a grain of sand.
Currently the whole earth (google maps data) is used to procedurally generate all the (extra) terrain, biomes, trees, grass, rocks and sand.
Check out some videos below:
Greeble City:
https://www.youtube.com/watch?v=jnqcSsEurBs
Tech demo:
https://www.youtube.com/watch?v=DfyMccDScAM
Trailer with space parts:
https://www.youtube.com/watch?v=Ql5chXOOQ4o
Beautiful mountain flight:
https://www.youtube.com/watch?v=8ANz50pBAdE