Strange minerals detected at the centers of impact craters on the moon may be the shattered remains of the space rocks that made the craters and not exhumed bits of the moon's interior, as had been previously thought. The foreign matter in the craters is probably asteroid debris and some could even be from Earth, which has thrown off its share of material as it's been battered by asteroids and comets over the eons. The discovery comes not from finding anything new in the craters themselves, but by planetary scientists who were looking at models of how meteorite impacts affect the moon. Specifically, the researchers simulated some high-angle, exceptionally slow impacts -- at least slow compared to possible impact speeds -- and they were surprised at what they found. "Nobody has done it at such high resolution," said planetary scientist Jay Melosh of Purdue University. Melosh and his colleagues published a paper on the discovery in the May 26 online issue of the journal Nature Geoscience. They found that when a slow enough impact happened, at speeds of less than 27,000 miles per hour (43,000 kph), the rock that struck doesn't necessarily vaporize. Instead, it gets shattered into a rain of debris that is then swept back down the crater sides and piles up in the crater's central peak. Read more http://news.discovery.com/space/ast...s/alien-debris-found-lunar-craters-130526.htm
