For some reason your scene setup, while seemingly simple, causes memory usage to skyrocket when attempting to render, regardless of the target resolution. I think it may have something to do with your odd Merge shader setup which doesn't quite describe a network loop, but has similarities that may be causing some kind of recursion problem. I would suggest you try making a copy of your Planet Surface Shader or using some other approach and see if that helps, but I can say with fair certainty that it is a problem in your network setup and not necessarily a bug per se.
- Oshyan
