The giant-collision theory of the moon’s origin just got blown out of orbit. Using a comparative analysis of titanium from the moon, Earth, and meteorites, researchers at the University of Chicago found the moon comes from just a single source: Earth.
The giant-collision theory holds that the moon formed after the Earth crashed into a Mars-sized object scientists dub “Theia” some 4.5 billion years ago.
If the theory were true, however, “Just like in humans, the moon would have inherited some of the material from the Earth and some of the material from the impactor, approximately half and half,” said Nicolas Dauphas, associate professor in geophysical sciences at UChicago, and co-author of the study, which appears in the March 25 edition of Nature Geoscience, in a press release.
“What we found is that the child does not look any different compared to the Earth,” Dauphas said. “It’s a child with only one parent, as far as we can tell.”
For the study, the researchers used titanium isotopes that are nearly identical. Titanium was the material of choice since it doesn’t typically turn to gas under intense heat. Titanium also has various isotopic signatures believed to date back before the sun’s birth.
“When we look at different bodies, different asteroids, there are different isotopic signatures. It’s like their different DNAs,” Dauphas said.
While there are large variations of Titanium isotopes in meteorites, lunar samples show “the moon has a strictly identical isotopic composition to the Earth,” he said.
Junjun Zhang, graduate student in geophysical sciences at the University of Chicago, one of the report’s co-authors, added, “We thought that the moon had two parents, but when we look at the composition of the moon, it looks like it has only one parent.”
Despite the discovery, however, the moon’s origin remains a mystery. Dauphas said “We thought we knew what the moon was made of and how it formed, but even 40 years after Apollo, there is still a lot of science to do with those samples that are in curatorial facilities at NASA.”
[box_light]Photograph courtesy of Lloyd DeGrane, illustration from the Public Domain[/box_light]