According to a study by geologists at the University of Toronto and the University of Maryland, the wealth of some minerals that lie in the rock beneath the Earth's surface may be extraterrestrial in origin, brought here by a rain of asteroids and comets. The extreme temperature at which the Earth's core formed more than four billion years ago would have completely stripped any precious metals from the rocky crust and deposited these metals in the Earth's core. The notion of an extraterrestrial origin my also explain another mystery, which is how the rock portion of the Earth came to have hydrogen, carbon, and phosphorous - the essential components for life. These minerals were also likely lost during Earth's violent beginnings.