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