Deliberate littering in space - and on a 100-stone scale. In July 2007, astronauts were told to throw an unneeded tank of ammonia weighing more than 100-stone from their shuttle. It had been part of the International Space Station's cooling system but it was no longer needed after a series of upgrades. Due to its huge weight, NASA did not want room wasted on the shuttle by carrying it back to earth. The 100-stone tank floated around for more than 12 months before hitting the Earth's atmosphere above the South Pacific and then burning up.