Stuart Wolpert, at UCLA Newsroom,
reports on UCLA-led research that
sheds further light on the creation of the Moon.
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Originally Posted by Stuart Wolpert, UCLA Newsroom
The moon was formed by a violent, head-on collision between the early Earth and a “planetary embryo” called Theia approximately 100 million years after the Earth formed, UCLA geochemists and colleagues report.
Scientists had already known about this high-speed crash, which occurred almost 4.5 billion years ago, but many thought the Earth collided with Theia (pronounced THAY-eh) at an angle of 45 degrees or more — a powerful side-swipe. New evidence reported Jan. 29 in the journal Science substantially strengthens the case for a head-on assault.
The researchers analyzed 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 — five from Hawaii and one from Arizona.
The key to reconstructing the giant impact was a chemical signature revealed in the rocks’ oxygen atoms.
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Originally Posted by Stuart Wolpert, UCLA
The fact that oxygen in rocks on the Earth and our moon share chemical signatures was very telling, Young said. Had Earth and Theia collided in a glancing side blow, the vast majority of the moon would have been made mainly of Theia, and the Earth and moon should have different oxygen isotopes. A head-on collision, however, likely would have resulted in similar chemical composition of both Earth and the moon.
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Originally Posted by Stuart Wolpert, UCLA Newsroom
“Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them,” Young said. “This explains why we don’t see a different signature of Theia in the moon versus the Earth.”
Theia, which did not survive the collision (except that it now makes up large parts of Earth and the moon) was growing and probably would have become a planet if the crash had not occurred, Young said. Young and some other scientists believe the planet was approximately the same size as the Earth; others believe it was smaller, perhaps more similar in size to Mars.
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The results have been published in
Science -
http://science.sciencemag.org/content/351/6272/493 (subscription required)
UCLA article here -
http://newsroom.ucla.edu/releases/mo...forming-planet (free)
