Space garbage

In the last 50 years the space exploration changed our lives: think only about GPS and satellite communications. But what happens with the satellites that are no longer in use? Some of them (the bigger ones) are driven back towards Earth and they burn in the atmosphere. But most of them are just left orbiting around the Earth. Thus the new place where garbage accumulates is in the space around our planet. This is more and more a concern because this kind of garbage can hit at any time a functional satellite or the ISS producing significant damage as satellites are designed to be as lite as possible, not resistant at impact with other objects. So now DARPA started to investigate ways to remove this garbage. Some more details here.