Map: Space Junk

People have been launching objects into space for almost 50 years, creating an ever-expanding orbiting junkyard. The United States now tracks more than 10,000 pieces of debris four inches wide or larger, but tens of millions of smaller fragments are also whizzing through space at speeds that can exceed 17,000 miles per hour, says Mark Matney of NASA's Orbital Debris Program. At such speeds, a collision with even an apple-size object could shatter a spacecraft into hundreds of pieces.