Space trash

On 10 February this year, a defunct Russian communications satellite crashed into an American commercial spacecraft, generating thousands of pieces of orbiting debris.

At the time, some observers put the odds of such an event occurring at millions, maybe billions, to one.

But experts had been warning for years that useable space was becoming crowded, boosting the possibility of a serious collision.

They have argued both for better monitoring of the space environment and for policies aimed at controlling the production of debris.

Over the past two years, a number of incidents have drawn attention to the problem of space debris.

In January 2007, China tested an anti-satellite weapons system by destroying one of its own spacecraft.

According to the US military, the A-sat test created 2,500 new pieces of debris which have been jeopardising satellites in the vicinity ever since.

In February 2008, the US used a sea-launched missile system to shoot down a wayward spy satellite loaded with fuel.

Then on 12 March this year, a close approach by a piece of debris measuring about 1cm (0.3in) forced the crew of the International Space Station (ISS) to shelter in their Russian Soyuz escape capsule.

There are thought to be some 18,000 objects larger than 10cm orbiting Earth, but millions more that are smaller.

Intact satellites share Earth's orbit with everything from spent rocket stages, tools lost on spacewalks and spacecraft wreckage to paint flakes and dust. They are the flotsam and jetsam of more than half a century of human activities in space.

At orbital speeds of 27,000km/h (17,000mph), even tiny pieces of debris can knock out a satellite or kill a spacewalker. And as the number of pieces of debris grows, so does the threat of collisions.

Read the full BBC article here