I think I might have done this story before – but due to another published paper. At http://wattsupwiththat.com/2014/06/05/when-worlds-collide-study-says-our… … we learn that a new bout of measurements of oxygen isotopes provides what is claimed to be evidence that the Moon was formed after a collision between the Earth and another, large, planet sized body. The theory is this occurred 4.5 billion years ago – Science journal (6th June, 2014) (see also http://phys.org/print321195253.html).
The research was conducted in order to confirm a prior hypothesis. The theory of the Moon's origin was as a result of computer modelling – which must call for a little bit of scepticism. The Moon is supposed to be composed of elements from both bodies – but how much of the Moon is Earth derived is open to question. The full research will be aired at the Goldschmidt Geochemistry Conference in California on June 11th – see http://goldschmidt.info/2014/
See also www.sciencemag.org/lookup/doi/10.1126/science.1251117 and http://phys.org/print269694905.html