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摘要

The Tunguska explosion, which in June 1908 leveled trees over a 5000-square-kilometer swath of Siberian forest, may have come from a much smaller meteorite than scientists had thought. A supercomputer simulation by scientists at Sandia National Laboratory in Albuquerque, New Mexico, showed that a much higher proportion of the total blast energy was transported to the surface than had been assumed. As a result, the team reported at last month's meeting of the American Geophysical Union in San Francisco, California, the explosion was likely between 3 and 5 megatons instead of the 10 to 20 megatons estimated earlier. Principal investigator Mark Boslough says the results suggest that small meteorites pose a greater threat to Earth than experts believed.