Small or large, personal or industrial—retrieving anything from space is immensely difficult, and has been done on just a handful of occasions. The military tracks about twenty-six thousand artifacts orbiting Earth, but its catalogue recognizes only objects larger than ten centimetres; the total number is much greater. By one estimate, there are a hundred million bits of debris that are a millimetre in size, a hundred trillion as small as a micron. We live in a corona of trash.