AST 309 Chapter Notes - Chapter 10: Kuiper Belt, Oort Cloud, Howardite
Document Summary
The leading theory for the moon"s formation: born when a mar"s sized body smacked into the infant earth some 4. 5 billion years ago. If this were the case the moon ought to bear the chemical signature of both. But a study suggests the moon"s isotopic composition reflects only. A mass spectrometer was used to make the measurement of the relative abundance of titanium 50 and titanium 47. The lunar ratio of the two isotopes is identical to that found in earth"s mantle, within 4 ppm. Simulations suggest that the second body would have contributed more than 40% of the moon"s bulk, so the ratio shouldn"t mirror earth so closely. But, titanium doesn"t vaporize as easily and it would have been more difficult for both bodies to have reached the same ratio. The fission model states that the moon was spun out of earth"s mantle early on, when the planet"s centrifugal force might have exceeded its gravitational force.
