The world that was formed in Genesis1:1 was formless and void according to Genesis1:2. This sounds like a good way to describe the indescribable. This leaves me to wonder, what was the nature of heaven in 1:1. Was it describable?
From what is said about the earth in that chapter, at that moment, no features of the planet were visible, only the thick water filled cloud over was visible from outside the planet. No light reached the surface of the planet yet. This surface was still too hot for water vapor to settle down as seas and was evaporated as soon as it touched the ground.
Since science tells us that the earth is quite a bit younger than the rest of the universe, our solar system was still in its infancy here. However, it seems reasonable to believe that the moon had taken its place however it was formed. Scientists still seem to debate how it came to be earth's companion.
There seems to be no consensus on how the moon came to be our companion, nor is it possible to know the mechanics of the early system from what I have searched.