For decades, scientists have accepted the explanation for the origins of the Moon involved a large Mars-sized object colliding with Earth. The result sent debris and other materials into outer space and over time it collected and coalesced into the Moon. They call this popular theory “The Big Splat,” and now there is evidence to compare the Moon’s origin to a quick hit-and-run car accident rather than a slowly moving head-on crash.
Apparently the Moon and the Earth have the same iron core. A recent analysis from the lunar samples taken from the Apollo Missions has shown very close similarities between the two. If the Big Splat Theory is true, then oxygen isotopes and isotope ratio of the metal titanium of the Earth and the Moon should be different.
Andreas Reufer, a scientist from the Center for Space and Habitability in Switzerland, has suggested that instead of a collision with a slow-moving object, a much larger and faster moving, sideswiping object hit the Earth. This new object would have lost only a small amount of material in the collision and would have continued on its way, like a hit and run car accident. This explains why the raw materials on the Earth and the Moon are so similar.
Dr. William K. Hartmann, one of the fathers of the Big Splat theory, believes this new theory builds upon his original theory rather than replacing it. Hartmann says:
An interesting thing is that the higher the velocity, the smaller the projectile needs to be. And the smaller the projectile, the higher the percentage of Earth material in the final swarm; this could help explain why the lunar material looks so Earth-like. On the other hand, it may be harder to preserve the tiny amounts of water that are turning up in lunar volcanic glasses, in a high-energy collision.
You can read the new study on the Hit-and-Run Theory in Nature Geoscience.