Evidence for Hot Cloud Theory of Moon Formation

Recent evidence by Alex Halliday of the University of Oxord shows that the commonly held theory surounding the Moon's creation - that the moon was formed when a Mars-sized object struck the Earth, may be incorect.

If the Moon was formed when an object the size of Mars struck the Earth, the Moon should mostly contain rock from the imacting boy. However, when Halliday's  team studied the ratios of light to heavy isotopes of various elements in rock from the Earth, Moon and meteorites they found that samples from both the Earth and Moon showed a preference for the heavy forms of iron and silicon. The Moon's isotopic make-up was identical to Earth's. There was no trace of an impacting object.

Halliday thinks that the results support a modified giant impact theory proposed two years ago by Kaveh Pahlevan and Dave Stevenson of the California Institute of Technology, Pasadena. They suggested that the impact of a Mars-sized body first created a hot cloud of rock vapour which mixed together as it cooled - obliterating any unique isotopic signatures of the impacting body - before forming the Moon.

Source: New Scientist