Scientists for the first time have been able to predict the arrival of an asteroid before it entered Earth's atmosphere.
The asteroid, estimated at 6 to 15 feet in diameter, entered the atmosphere over Sudan on Tuesday morning, providing a brilliant light show in East Africa as it burned up.
Scientists said it posed no threat to people on the ground, though some tiny pieces may have reached the Earth's surface.
The important thing, scientists said, was not the discovery of the object, but the prediction of its trajectory.
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The object was first spotted Monday morning by the Catalina Sky Survey telescope near Tucson, Ariz. At the time, the object was outside the moon's orbit. Data from the observation was shipped to the Near-Earth Object Program Office at the Jet Propulsion Laboratory in La Canada Flintridge, Calif.
“We did an impact analysis and saw that it would indeed hit” the Earth, or at least its upper atmosphere, said Don Yeomans, director of the office charged with monitoring space rubble.
Yeomans then alerted space observers around the world, including the U.S. Department of Defense.
Although advance notice of less than a day would hardly be enough time to prepare for the arrival of the kind of asteroid believed to have wiped out the dinosaurs 65 million years ago, Yeomans said the successful prediction “shows the system is working.”
One reason the object wasn't spotted earlier, according to Yeomans, was that it was “at the lower end of what we can discover.”
An object large enough to do serious damage to Earth and its creatures would presumably be seen much earlier.