I know you can do it. Part of the fun in writing fantasy or science fiction is that we get to explore different worlds. I've read a number of tales that feature one or more imaginary planet. They don't have to share all of the details but certain elements that are within the scenes are great to help give the reader an image to spark their imagination.

If you don't figure it all out yet, maybe you can do more world building between drafts. It is possible to do draft one and not know everything about the world. We are here to cheer you on too.