Mystery Solved! Moon Came From Earth's Tidbits, Study Reveals

A new chemical study published in Nature has just confirmed how the moon was formed.

As mentioned by ZME Science, the most popular theory about Earth's formation is the giant impact hypothesis, which was first proposed in the 1970s. It states that the moon was formed by a grazing collision between the proto-Earth and a Mars-sized body called Theia. The debris from both bodies eventually formed the moon.

In 2001, however, geochemists have found out through rock samples brought by Apollo astronauts that the isotopic compositions of the terrestrial and lunar rocks are nearly identical. Now, this is quite improbable if the moon's composition came from Earth and the impactor since the two planetary bodies formed in different parts of the solar system with the same isotopic compositions is unlikely.

Washington University in St. Louis geochemist Kun Wang, and Stein Jacobsen, professor of geochemistry at Harvard University, used this as a starting point of their study.

In a press release, Wang said many scientists have tried to explain the isotopic composition using the theory that the collision was a low-energy impact. It was only in 2015 when a model suggested that the collision was actually violent.

"So people decided to change the giant impact hypothesis," Wang said. "The goal was to find a way to make the Moon mostly from the Earth rather than mostly from the impactor. There are many new models-everyone is trying to come up with one-but two have been very influential."

"They're trying to explain the isotopic similarities by addition of this atmosphere," Wang said, "but they still start from a low-energy impact like the original model."

Using a method that is 10 times more precise and accurate than the previous methods used by scientists, Wang and Jacobsein have shown a potassium isotopic evidence supporting the 2015 model, that the collision which was initially thought to be low-impact was actually violent and the Earth was actually vaporized.

As noted by Popular Mechanics, the scientists analyzed a total of eight terrestrial samples and seven lunar rocks. They found out that lunar rocks have an abundance of the heavy isotope potassium-41, suggesting that the material from Earth was actually vaporized. This would not have occurred in the lower-energy impact theory, it says.

The collision was wild enough that most of the moon was once part of the still-forming Earth.