Most astronomers believe that the Moon formed when a Mars-sized object struck Earth. If this is the case, the Moon should contain mainly rock from the impacting body. However, Alex Halliday of the University of Oxford and his colleagues have evidence suggesting that this isn't so. The team studied the ratios of light to heavy isotopes of various elements in rock from the Earth, Moon and meteorites. The Moon's isotopic make-up was identical to Earth's, with no trace of an impacting object. Halliday thinks that the results support a modified giant impact theory. They suggested that the impact of a Mars-sized body first created a hot cloud of rock vapour. This mixed together as it cooled - obliterating any unique isotopic signatures of the impacting body - before forming the Moon.
Thanks to Shaun A. Saunders for the post
Thanks to Shaun A. Saunders for the post
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