According to NASA's Orbital Debris Program Office there are tens of millions of debris particles orbiting the earth. About 17,000 of these are over 10 cm , orbit within 2,000 km of the Earth and are routinely tracked by the US Space Surveillance Network. The average speed is about 36,000 kmph.

Up until 2007, the amount of debris and rate of break-up and increase was all fairly predictable for NASA who had assumed the role of space "groundskeeper". But then in January 2007 the Chinese said their Fengyun 1C spy satellite was malfunctioning; so they blew it up.

The US condemned the Chinese missile strike saying space should be used for civilian purposes and not military displays. According to NASA's Orbital Debris Program Office (see http://orbitaldebris.jsc.nasa.gov/) the Chinese had caused the worst orbital debris cloud in history. About 35,000 pieces of junk were splattered into space.

The US pointed out that they had not used military weapons in space since 1985 when they had blown up their P78-1 satellite and then been condemned by the scientific community.

This 22 year armistice faltered after the Chinese attack. Just a few weeks later, on February 21, the US explained that one of their spy satellites (the USA 193) was also malfunctioning. So they shot it down.

The US said the timing was not in response to the Chinese missile strike and was instead purely coincidental. The US also pointed out their SM-3 missile cost about USD10 million, travelled at over 36,000 kmph and resulted in nearly all of the debris burning up on re-entry. What's more the whole display was publicised thanks to a Pentagon video display. Touche China....