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In pictures: How to protect Earth from asteroid de...
NASA detects, tracks and characterizes asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near Earth Object Observations program, commonly called "Spaceguard," discovers these objects, characterizes a subset that are of interest and plots their orbits into the future to determine whether any could be potentially hazardous to our planet. As of Feb. 1, 2014, 10,685 NEOs have been discovered, including about 97% of asteroids larger than .6 miles (one kilometer). But there is a greater need to pinpoint smaller asteroids such as the one that exploded near Chelyabinsk, Russia, NASA said.
In pictures: How to protect Earth from asteroid destruction