Read Heaven at SETI's Doorstep Page 6


  * On Earth and in the composition of other planets, the heavier elements are normally found in the core while the lighter materials are concentrated at the surface. But not so with the Moon. The abundance of refractory elements like titanium in the surface areas is so pronounced, that several geologists proposed that the refractory compounds must have been brought to the moon’s surface in great quantity in some unknown way. They are adamant. They don’t know how, but there is no other way for this to have happened!