Exploding Asteroids Pose Greater Threat Than Direct Hits
An "airburst" warning scale is needed for asteroids, cautions one expert.
An asteroid bursting apart in midair over a city poses a greater threat to humanity than a long-feared "planet buster" smacking into Earth, suggests one impact expert. He calls for a revised system of planetary defense focused on detecting smaller asteroids, instead of the big ones.
Earth orbits amid a shooting gallery of meteorites and asteroids; such shooting stars can be seen crossing the sky every 15 minutes on a typical night. (See "Tips for Enjoying the Perseids Meteor Shower.")
Sometimes those space visitors are larger, such as the February 15 fireball that exploded over Chelyabinsk, Russia, injuring some 1,500 people in six cities across the region, or the 1908 Tunguska event that flattened 830 square miles (2,150
