Space.com says scientists are making so much progress finding and tracking big, dangerous space rocks that a surprise civilization-threatening impact is becoming less and less realistic.
It's highly unlikely, for example, that a 6-mile-wide (10-kilometer) near-Earth asteroid — the size of the space rock thought to have wiped out the dinosaurs 65 million years ago — lurks out there undiscovered, researchers say.
Asteroids much smaller than the dino-killer could still inflict catastrophic damage if they slammed into Earth. In general, scientists think a strike by anything at least 0.6 miles (1 km) wide could have global consequences — most likely by altering the world's climate for years to come.
Observations by NASA's infrared WISE space telescope recently allowed astronomers to estimate that there are about 981 of these mountain-size asteroids on orbits that bring them relatively close to Earth.
That number may sound scarily large. But sky-scanning researchers have already found and cataloged nearly all of them.
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