"We're at what we call a 'critical density' — where there are enough large objects in space that they will collide with one another and create small debris faster than it can be removed," Kessler recently told Marketplace.
For nearly 20 years, Kessler (who was retired until very recently) lead NASA's Orbital Debris Program Office, which keeps track of all the growing clutter around Earth.
He predicts that eventually, there will be so much space junk that leaving Earth to explore deep-space will be impossible. That includes sending satellites to distant stretches of the solar system, like Pluto, and manned-missions to Mars.
Something must be done, he says. So he's come out of retirement to help find a solution.Read More: Yahoo Finance