Tardigrades can survive the vacuum of outer space.

Tardigrades, microscopic eight-legged animals sometimes called water bears, are among the toughest creatures known. In 2007, the European Space Agency sent dehydrated tardigrades into low Earth orbit aboard the FOTON-M3 mission and exposed them directly to the vacuum of space and unfiltered solar radiation for about 10 days.

When rehydrated back on Earth, a portion of the tardigrades revived, and some went on to reproduce normally. They survive this kind of exposure by entering a dormant state called cryptobiosis, in which they expel almost all the water from their bodies and drastically slow their metabolism, essentially pausing life until conditions improve.