Which symbolizes our very moon where one of the three theories of mainstream science of the origin of our moon is exactly that. The moon being a part of planet earth and getting separated and becoming earth's satellite.

They call it fission.

The cities on top of that rock in avengers symbolizes that the moon is inhabited on its dark side.

Google in images "comet empire" to get a more accurate picture. It's from an anime but it nails it.