What happened when the moon 'turned itself inside out' billions of years ago?

Over 4.2 billion years ago, the moon turned itself inside out to create the lunar surface that has become familiar to humanity.

Most scientists would agree the moon was created around 4.5 billion years ago, when another massive body in the solar system smashed into Earth, flinging molten material into space that coalesced as our natural satellite.

How the birth of the moon proceeded after this violent start, however, has been described as "more of a choose-your-own-adventure novel" by a team of scientists from the University of Arizona's Lunar and Planetary Laboratory (LPL).

They say there are many possible paths Earth's natural satellite could have taken to form in full, ultimately leading to the moon-Earth system we see today. The team of course has its own ideas about the major incidences that might have formed the moon. The researchers say rock samples collected during the Apollo mission, for instance, may indicate there was a time when the moon "flipped inside out."

This result, if true, might also solve a lingering mystery about the moon's composition.

"Our moon literally turned itself inside out," research co-author and LPL associate professor Jeff Andrews-Hanna said in a statement. "But there has been little physical evidence to shed light on the exact sequence of events during this critical phase of lunar History, and there is a lot of disagreement in the details of what went down — literally."

Related: Humans are changing the moon's surface so much it's entered a new geological era, scientists say