We're surrounded by space junk. Every time we head up or come back, we leave bits and pieces behind. Everything from tiny fragments to whole satellites are flying around up there. The junk has already begun to cause problems and will only get worse if we don't clean it up. Now, scientists are looking at ways to bring the junk down.

One idea involves launching a "space harpoon" to pull junk into a downward-spiralling orbit that allows it to safely burn up in the atmosphere. The harpoon needs to be strong enough to penetrate the outer skin of the dead satellites and spacecraft, but not so strong to cause the junk to break into more pieces. via BBC News