While trying to find more information on this new model/theory, I found another one: http://news.psu.edu/story/317841/2014/06/09/research/55-year-old-dark-side

While trying to find more information on this new model/theory, I found another one: http://news.psu.edu/story/317841/2014/06/09/research/55-year-old-dark-side-moon-mystery-solved http://news.psu.edu/story/317841/2014/06/09/research/55-year... Which purports that the difference was created due to tidal locking and a temperature gradient in the early formative years of the Earth and Moon.