Can we clean up space?

Forget oil spills and greenhouse gas emissions, our amazing ability to mess up the environment now extends well into space. Yesterday, the Guardian published an image from the European Space Agency of the masses of space junk orbiting Earth. Our diminutive planet was hard to make out through the clouds of cosmic debris.

According to Nasa's orbital debris programme, around 17,000 objects with a diameter larger than 10cm (4in) are tracked to make sure they don't damage orbiting satellites and the International Space Station (ISS). Nasa reckons there are more than 200,000 objects between 1cm-10cm and tens of millions smaller than that.

Where does it all come from? Much of the orbiting scrapyard is defunct satellites, launch vehicles, rocket stages and even flecks of paint. From time to time the fuel in derelict spacecraft causes an explosion, creating a shower of new fragments. When two pieces hit each other they produce even more. Some of it is produced deliberately. Last year the ISS crew jettisoned a fridge-sized tank containing ammonia that was part of the cooling system. And both the US and China have fired missiles from the ground to destroy satellites. The tackiest and most pointless addition came in November 2006 when Russian cosmonaut Mikhail Tyurin edged out into space to hit a golf ball into the abyss as a promotion for a sports company.

So what can we do about it? Not much. Blowing things up just creates more debris, so the only practical option is to wait until a piece of junk's orbit spirals close enough to Earth for it to burn up in the atmosphere. Debris in orbits below 600km (370m) typically falls back to Earth within a several years, but above 1,000km (620m) our rubbish stays up there for more than a century. At the moment, though, we are creating space junk faster than it is destroyed.