Tardigrades can survive the vacuum of outer space

Tardigrades — microscopic animals less than 1 mm long, also called 'water bears' — are the most resilient animals known. In 2007, the European Space Agency sent tardigrades into orbit exposed to the vacuum and radiation of open space for 10 days. Upon return, 68% of those shielded from cosmic radiation survived, and some even reproduced. Tardigrades survive by entering a state called cryptobiosis, expelling nearly all water from their cells and reducing metabolic activity to 0.01% of normal. They can survive temperatures from -272°C to 150°C, pressures six times that of the deepest ocean, and radiation doses 1,000 times the lethal human dose.

Source: Jönsson et al., Current Biology (2008)