Where humans go, garbage tends to follow—and space is no exception.
And much like the buildup of trash on Earth, the accumulation of junk in space poses a problem for future generations. Orbital debris, or space junk, is already posing direct threats to satellites and spacecraft: The International Space Station already has to sidestep dangerous pieces of trash, and satellite launches already have to factor debris into their timetables.
All the spacefaring nations are trying to find ways to clean up the mess before the ever-growing clutter makes launches impossible. Here’s an introduction to the garbage orbiting hundreds of miles above your head: