The Cosmic Origin of Mineral Deposits
Vast quantities of cosmic material, ranging in size from fine dust to large meteorites and planetoids, have been colliding with and accumulating on the earth since its origin 4.5 billion years ago. There are less than twenty well preserved meteorite craters and less than thirty fossil craters or astroblemes on the present face of the earth. On the moon, there are approximately 200,000 craters on the visible face alone - the largest crater being 132 miles in diameter and attaining a depth of 16,000 feet. Making allowances for the different physical conditions on the moon and assuming that these lunar features are of impact origin, the inference is that, since primeval time, large numbers of celestial objects have also encountered the earth, but that both the topographic expression of the impact and the objects themselves have been destroyed by weathering .and erosion.
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