Evidence Against Moon as Meteoroid’s Offspring

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Source:  Sindyan N. Bhanoo, The New York Times
Excerpt: Astronomers have long theorized that the Moon was formed when an object the size of Mars slammed into Earth, sending a huge mass of rock into orbit around it. “According to the prevailing model prediction, approximately half of the Moon-forming material should come from the Mars-size impactor,” said Junjun Zhang, an isotope geochemist at the University of Chicago and the study’s first author. But samples of isotopic titanium from the Moon and from Earth now suggest that material from Earth is predominant on the Moon, researchers report in the journal Nature Geoscience. …She and her colleagues used lunar samples gathered by the Apollo missions in the 1960s and ’70s. They compared the isotopic titanium ratio in these samples to that of samples from Earth. The researchers also found that meteorites have a much wider range of isotopic titanium. “That also tells us that the impactor that hit the Earth was very unlikely to have to the same composition as the Earth,” Ms. Zhang said. “So the prevailing model of the giant impact probably needs to be revisited.”…. 

 http://www.nytimes.com/2012/04/03/science/new-insight-on-moons-origins.html

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