Proof of Moon’s Birth in Giant Impact Found in Zinc: Study
Water on the moon boiled away in massive quantities in a cataclysmic evaporation event during the moon’s birth, bolstering the theory that a Mars-sized body collided with the Earth to form its only natural satellite, scientists say.
Image: This artist’s conception of a planetary smashup whose debris was spotted by NASA’s Spitzer Space Telescope three years ago gives an impression of the carnage that would have been wrecked when a similar impact created Earth’s Moon. A team at Washington University in St. Louis has uncovered evidence of this impact that scientists have been trying to find for more than 30 years. Image released Oct. 17, 2012. Credit: NASA/JPL-Caltech
Researchers examined rocks collected by astronauts during NASA’s Apollo lunar landing missions, as well as a meteorite that originated on the moon to make the find. They looked for traces of zinc, and found the ratios of heavy to light isotopes are greater than on Earth, which suggests the moon went through an intense evaporation event early in its formation.
The study is more evidence for the theory that the moon formed from a colossal impact, researchers said.
Early in the moon’s formation, the surface was hot enough to vaporize zinc – and a giant impact is one of the few things that would generate that much heat. Another prediction of the theory is that heavier isotopes would be more common, because they would condense at a higher temperature.
“What we found is that the depletion [of lighter isotopes] of Zinc is probably due to evaporation,” said study co-author Frédéric Moynier, assistant professor of Earth and planetary sciences at the Washington University in St. Louis.