Perhaps due to the fact that it is the largest celestial object in our skies, the moon has long fascinated mankind. Many civilizations around the world have their own folklore about the effects and powers of the Moon, some of which veer into the bizarre. Origin stories about the Moon are innumerable and vary widely from culture to culture.
One of the more long-standing scientific hypotheses has been the Giant Impact Hypothesis, which posits that a collision between the Earth and a large celestial body was the catalyst for the Moon’s creation. There are two somewhat opposing views on this theory however: a low-energy model in which the moon was formed by the debris left from the object which impacted into Earth; and another high-energy model in which the impactor object was vaporized entirely, leaving a cloud of Earthly debris to eventually form into the moon.
A 2001 study found that much of the chemical composition of the Moon matches that of Earth, but was not definitive enough to reach a definite conclusion to the debate over the Giant Impact Hypothesis. A new study published in Nature might put that debate to rest, however.
A team of researchers from Washington University in St. Louis has released data from recent chemical analyses of potassium isotopes found on both the Moon and Earth which, they contend, prove that the Moon formed from Earth debris released in a high-energy impact. According to their research, these analyses show that the Moon was created from debris released from Earth’s “proto-mantle,” the largely silicon-based molten layer of rock beneath the surface of what was then the still-forming Earth:
Our K isotope result is inconsistent with the low-energy disk equilibration model, but supports the high-energy, high-angular-momentum giant impact model8 for the origin of the Moon.
Lunar soil is depleted of certain potassium isotopes, while the Earth’s soil is rich with them. This fact has confounded scientists and astronomers, but this new research shows that the only explanation must lie in the aftermath of a volatile high-energy impact. Thus, it would seem that the Moon was once part of our Earth.
This connection might explain the immense cultural significance of and fascination in the Moon found throughout the world; we are of the Earth, after all. Perhaps deep down inside our molecular consciousnesses, we long to be reunited with our missing potassium isotopes. Or we’re just fascinated by the fact that there’s a giant glowing orb in the sky that comes out every night. Let’s go with that.