Asteroid 2012 DA14 buzzes and misses Earth
By comparison, NASA estimated that the meteor that exploded over Russia was much smaller – about 49 feet (15 meters) wide and 7,000 tons before it hit the atmosphere, or one-third the size of the passing asteroid.
As for the back-to-back events, "this is indeed very rare and it is historic,'' said Jim Green, NASA's director of planetary science.
"These fireballs happen about once a day or so, but we just don't see them because many of them fall over the ocean or in remote areas. This one was an exception.''
As the countdown for the asteroid's close approach entered the final hours, NASA noted that the path of the meteor appeared to be quite different than that of the asteroid, making the two objects "completely unrelated.'' The meteor seemed to be traveling from north to south, while the asteroid passed from south to north – in the opposite direction.
Most of the solar system's asteroids are situated in a belt between the orbits of Mars and Jupiter, and remain stable there for billions of years. Some occasionally pop out, though, into Earth's neighborhood.
NASA scientists estimate that an object of this size makes a close approach like this every 40 years. The likelihood of a strike is every 1,200 years.
The flyby provides a rare learning opportunity for scientists eager to keep future asteroids at bay – and a prime-time advertisement for those anxious to step up preventive measures.