The moon was formed by a violent collision between the early Earth and a “planetary embryo” called Theia, according to new research.
While scientists had already known about this high-speed collision, it was long thought that the collision was at an angle of 45 degrees or more rather than head-on.
When the ancient planet, Theia, smashed into Earth, it blasted debris into space. The moon formed out of that debris.
Planetary scientists first came up with this theory in the wake of the 1969 Apollo moon landing, offering an explanation for why our world has such a massive moon.
It was previously thought that the moon was formed mainly from Theia, but new data suggests it was a mixture between the two planets.
Geochemists from the University of California, Los Angeles also discovered that some of the water on Earth today may have come from Theia.
The findings from the new study were made by analysing seven rocks brought to the Earth from the moon by the Apollo 12, 15 and 17 missions, as well as six volcanic rocks from the Earth’s mantle.
[Image: Southwest Research Institute]
"The new measurements presented here are consistent with Earth and the Moon having near-identical Theia contents,” says Dr Edward Young, lead author of the new study and a UCLA professor of geochemistry and cosmochemistry.
“This suggests that the moon-forming impact thoroughly mixed and homogenised the oxygen isotopes of Theia and proto-Earth.”
The second question is why the far side of the moon is so much more mountainous and thick-crusted than the side we see.
But for now, the moon holds on to its mystery.