Chelyabinsk-sized Asteroid Impacts May Happen More Often Than Previously Thought

On Feb. 15, 2013, a small asteroid collided with Earth. It came in over Russia at a low angle, slamming into our atmosphere, violently compressing the air in front of it. That created a vast amount of heat and pressure, which simultaneously melted and broke up the asteroid into smaller fragments. Within seconds, the huge energy of motion of the rock was suddenly and violently dissipated, creating an explosion equal to about 500,000 tons of TNT detonating. The resulting shock wave swept down over...