Space junk is all the stuff that humans have left in Earth’s orbit, such as abandoned spacecraft, satellites, launch vehicle stages, and mission-related debris. As we put more and more stuff into space, there is a higher chance of this stuff colliding. Collisions of space junk create more and more pieces that can go on to cause more collisions, potentially enveloping the Earth in a wall of space junk. This could interfere with or even destroy operational spacecraft including satellites. If the problem becomes serious enough, we could lose the capability to launch anything into space to clean up the mess.