At speeds averaging 6 miles per second, even the smallest fragments can punch holes in the armor of spacecraft, and anything larger than a few inches will cause total destruction on impact, creating even more debris. In 1978, NASA scientist Donald Kessler predicted that these types of impacts would give way to something more serious--a domino effect of collisions in Earth's orbit that would make space flight impossible for generations.

Scientists are now scrambling to undo the damage caused by decades of space littering--designing satellites that withstand impacts, spacecraft that dump additional propellant to minimize explosions, and upper stages that maneuver into storage orbits at the end of their active lives. Whether these and other measures can keep us from Kessler's future, however, remains to be seen.