The science community has long believed that Earth collided with another large planet called “Theia.” The collision was thought to be more of a sideswipe, but UCLA researcher Edward Young and his team found evidence to the contrary.
Rock samples from three Apollo missions and volcanic rocks from five locations in Hawaii and Arizona were studied. To determine similarities and differences, Young and other UCLA researchers compared the chemical signatures of the oxygen atoms in the rocks they studied. Instead of finding large differences, the rocks’ compositions were surprisingly similar.
“We don’t see any difference between the Earth’s and the moon’s oxygen isotopes; they’re indistinguishable,” Young said. This means both the Earth and the Moon are made up of the same material, and thus Theia and Earth’s composition were well mixed.
Think of it this way: Had Theia struck indirectly, the Moon would have been composed more of the remnants of Theia, and less of Earth debris. The fact that the chemical compositions of both the Earth and the Moon are so similar makes it fairly likely that the two planets had a near direct, possibly head on, impact.
No parts of Theia survived the impact, and it’s believed that the planet would have continued to form and reached near-Earth size at maturity. The fact that Theia was completely destroyed also lends credence to Young’s theories, for sure.
While Young’s research is groundbreaking, it doesn’t come without controversy. His team’s results are in direct contradiction with a 2014 study by a team of German scientists. Their results found a difference in the chemical compositions of Earth and Moon rocks, although ever so slight.
Even with the contradicting results, UCLA’s study still adds credibility to the idea that the Moon is the result of some type of cataclysmic collision rather than the Earth’s capture of a foreign body, which at one point was considered a reasonable hypothesis.
