Humans are an extremely messy species. We can't seem to go anywhere without polluting or somehow contaminating an environment. However unlikely it may seem, we even managed to do that with space. Through our adventures into the final frontier, we managed to leave a lot of junk just floating around our planet. Literally tons of material has been left out there, anywhere from entire dead satellites to tiny chips of paint. Fortunately, this isn't a terrestrial environment so our pollution isn't harming any animals, except us.
For an object to stay in orbit it must necessarily be going very very fast. Even extremely tiny objects that are moving that fast can cause a lot of damage if they hit anything. This can pose a risk for any humans in orbit, as well as damaging existing satellites and other structures in space. Cleaning up this mess is extremely challenging as the targets are, again fast, a wide variety of sizes, and extremely disperse. But a team led by scientists from Japan believe they have found a potential solution. (via Engadget)
Their solution is elegant in its simplicity, blast everything with a laser. Yes their hope is to take an extremely powerful fiber-optic laser, normally used to power particle accelerators, and mount it to the International Space Station. They suspect that this system could have a range of 100 km and could target something as small as a centimeter in diameter. And this is all thanks to their proposed targeting system, utilizing the Extreme Universe Space Observatory, an already existing infrared telescope.
First they want to install a proof of concept system on the ISS. With only a 20 cm telescope for targeting and a laser with approximately 100th the power. If that works though, the next stage is the full powered laser with the full-sized telescope. Mounting it on the ISS, they believe they could eliminate approximately 3000 tons of material. Despite the power of the laser, it wouldn't actually vaporize many of the targets, just hit them enough to degrade the orbit, causing it to reenter Earth's atmosphere.
While 3000 tons seems like alot, that's only the junk in range along the path of the ISS. The ideal final step to a project like this would be a standalone satellite equipped with an equivalently powered telescope and laser. Putting such a satellite in a polar orbit would allow it to almost entirely cover the orbital space of the earth.