Space junk is a real problem. NASA now tracks around 20,000 pieces of debris orbiting Earth, most of them larger than 10 cm across. Since the average speed of a collision between orbiting objects is 10 km/s these pieces of trash can cause a lot of damage despite their small size.

Scientists in Switzerland have a plan to clean up space junk - it involves creating a 'Janitor Satellite' that will seek out pieces of space junk to drag back into the atmosphere causing them to burn up.

For more information visit http://www.abc.net.au/catalyst.

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