The Air Force has a catalog which contains almost 19,000 pieces of orbital debris. This numbers was increased by 600 this week, after an American Iridium and a Russian Cosmos collided. The two satellites crashed on Tuesday high above Siberia and have left the space polluted with the flotsam and jetsam of a satellite-dependent civilization.

The collision implies other risks, such as the endangerment of the Hubble Space Telescope and other communications satellites. These might be hit by an object moving at hypervelocity at any time. But the military radar can detect objects which measure four inches in diameter and which have the size of a softball.

The crash from Tuesday produced a lot of small and undetectable pieces of debris which may be still carrying kinetic punch which could damage or destroy a spacecraft. Nicholas Johnson, NASA's chief scientist for orbital debris, stated that they expect there to be thousands of pieces which could measure centimeters of even millimeters.

Yet, some small pieces of debris have always been wandering in space. And we should remember about the defunct satellites which nobody went to recollect after they had finished their missions. The oldest satellite that just stands in the space is the Vanguard I satellite launched by the United States in 1958.
 
For example, China made a lot of mess in the outer space in January 2007 when they destroyed an old satellite as to prove the strength of another projectile. But, as Johnson said, the projectile converted the satellite to nearly 2,500 fragments.