A rock from space about 55 feet across (17 meters) entered Earth's atmosphere early on the morning of Feb. 15, 2013.
Before entering the atmosphere, the object weighed about 10,000 tons. An early estimate of the energy of the Russian meteor explosion is that it equaled about 30 atomic bombs of the type used on Hiroshima in World War II.
The Russian meteor is second only to an explosion that occurred in Siberia in 1908. In the so-called Tunguska event, a 130-foot-wide (40 m) object exploded, flattening trees over an 825-square-mile area (2,137 square km). Even larger impacts from space occurred before recorded human history.
The solar system was shaped by even bigger impacts from space. Fifty thousand years ago, a rock about 150 feet wide (46 meters) crashed into what is now Arizona. The crater is 0.7 mile in diameter (1.2 km). Impacts have occurred since the beginning of our solar system. In 1994, the planet Jupiter was assaulted by fragments from comet Shoemaker-Levy 9.
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