According to a report here and a statement made by a Russian Space Forces official, the International Space Station may have suffered a minor collision with a piece of space debris. Astronauts awoke to the gut-wrenching sound of metal scraping against metal, which lasted for a period of about one second. However, subsequent examination with an externally-mounted camera revealed no sign of damage, leading authorities to believe the sound was caused by equipment shifting internally.

This incident brings back memories of Mir's near-disaster collision with the Progress resupply vessel, back in 1997. While there is a Russian Soyuz escape vessel permanently docked to the ISS, strange sounds are not the nicest thing to wake up to in a vacuum.

Despite assuasions by the Russian authorities, the incident doesn't quite add up. The typical velocity of a piece of space junk 11mm in diameter is around 5.71kms^-1, so an external impact of anything larger than a fingernail would tear a hole in the side of the craft large enough to depressurise the cabin - which doesn't seem to be the case. This leads to the conclusion that a sound akin to a tin can being crushed eminated from the interior of the cabin, which we can assume is not something regularly associated with life on board the ISS (this isn't Skylab, after all).

It's a sobering thought that the amout of space junk in high orbit around this planet is increasing rather rapidly, with millions of tiny, hull-piercing projectiles whizzing around as frictionless flotsam. If internal movement was to blame, hopefully there was no serious payload failure aboard the USD $90bn scientific laboratory.