Spider escapes from experiment on space station 11/19/08
Two spiders and some painted lady butterflies were launched into space on the space shuttle, as part of an experiment for school children. They wanted to see if the orb-weavers could spin a straight web without gravity to guide them. But one of the spiders apparently escaped in the space station--at least, it wasn't to be seen in its cage.
I'm going to be looking for more examples of varmints in space in the next few days. It's just a matter of time until cockroaches make it to the moon. Then what?
All kidding aside, for many years, contamination of the moon and mars from hitchhiking bacteria has been a serious concern. There was always a possibility that bacteria could survive the trip, then multiply on mars, making it impossible to find out if life had evolved on Mars on its own.
In one study, they took apart some manmade object that had been retrieved from the moon or from space, and actually found a microbe that had survived the long exposure to space.
The theory that life on earth arose from a microbe hitchhiking in from some alien planet on a meteor--is called "panspermia." A bit like the Superman story.