Space Junk

"Space Junk Orbiting Our Planet Has Become a Big Mess":

NASA estimates that more than 100 million man-made objects the size of a grain of salt are orbiting the planet. About 500,000 objects that are roughly the size of a marble are also believed to be out there, as well as 23,000 objects the size of a softball or larger.

The amount of such fragments has expanded exponentially since the dawn of space exploration in the early 1960s. It has primarily resulted from discarded rocket parts and satellites, as well as from smash-ups between chunks space junk over the years — much of the debris is made up of bits of other debris. This phenomenon is known as the Kessler Syndrome, named for NASA scientist Donald Kessler, who described the effect in 1978.