Okay, there has been speculation for decades that the Moon was once part of Earth and that a Mars sized cue ball hit the Earth with such force that it knocked part of the Earth out of atmosphere forming the Moon. As this all happened 4.5 billion years ago there are no eye witness accounts available.
What makes this interesting now, is the theory, or discovery, that the Moon had fountain volcanic activity. That is only possible with oxygen. So the question arises: Did the Moon have oxygen of its own to create such activity? or, was the activity preexisting before it separated from Earth? Inquiring minds want to know. Doc