Debris in space, which has been accruing since the 1950s, is a well-documented problem. NASA estimates there are roughly 22,000 objects larger than 10cm in diameter in near-Earth orbit. There are likely tens of millions of smaller pieces, too. Most of this junk is moving at extremely high speeds – up to seven times the speed of a bullet. At that speed, an object no bigger than a penny could easily destroy a spacecraft. 

Read more at Science Focus.