Next month, Japan's space agency (JAXA) will launch a space trawler -- a spacecraft that will drag a giant aluminium and steel net while orbiting Earth, hoping to bag itself some space junk. NASA tracks around 20,000 pieces of larger (5cm+) orbital debris, but there's an estimated 500,000 pieces of marble-sized, untrackable debris in orbit as well. If a single piece of space junk hits an orbiting, functional spacecraft, the collision is likely to be catastrophic -- just like in the movie Gravity. If we don't get on top of orbital debris now, it's feared that one day the junk will be so dense that we won't be able to leave the surface of Earth without being smashed to pieces.