First, the Moon does not have an iron core. This pretty much rules out that it coalesced from the same cloud of debris that the Earth did.:') That is evidence in support of capture. The apparent lack of an iron core -- the Earth's is 90 per cent iron, with about 10 per cent other stuff -- also suggests it wasn't born of the Earth, but obviously, either through an impact or an overspin one could suppose it would be made of core material. It would indicate a formation further out in the solar system.
If the Moon were captured, it too would not match the Earths oxygen isotope ratio...There's no reason to expect it wouldn't -- the supposed impactor would contribute some (http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1669.pdf assumes 50 per cent) of the lunar material, which means the supposed impactor must have had oxygen isotopes essentially identical to those of the Earth. It's simpler to say, there were two, not three. In addition, the lunar surface has been under bombardment continually for billions of years, and the oxygen isotope ratios of the incoming material must have had no contaminating effect at all.
George W. Bush will be reelected by a margin of at least ten per cent
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