It is the biomeExtractor class
New version of the map generator has been released
I decided to pull up the water settings for some biomes in the editor, and compared to the default, it looks like the values for lerp/sky reflections/sun strength are generally higher, and the surface colors are generally blackened. I might make a pr that makes some adjustments...
Default:
Mars:
Syrtis:
Stones:
pfp credit to gieb