"New research suggests that space rocks as large as the one that fell over Chelyabinsk -- about 19 meters (62 feet) across -- are three to five times more numerous than scientists had realized. The study, led by Peter Brown at the University of Western Ontario, also found that larger and more dangerous ones are unexpectedly abundant. In other words, alien projectiles pose a serious threat. Is it a manageable one?"
On Feb. 15, a 13,000-ton rock plunged through the skies above Chelyabinsk, Russia. It shone 30 times brighter than the sun, and hurtled at 42,000 miles per hour toward a city of more than a million people.
As the rock broke apart during its fiery descent, it dispersed energy equivalent to 500 kilotons of TNT, shattering thousands of windows. Some 1,500 people were injured, and shock waves caused a ribbon of damage extending 55 miles on either side of the meteor's path. Witnesses thought a nuclear war was upon them. Luckily, no one died.