Tardigrades survive the vacuum of space

In 2007, scientists strapped a few thousand tardigrades to the outside of a satellite, opened them to the vacuum of space, and ten days later brought them home alive.

Tardigrades are microscopic, eight-legged animals - half a millimetre long, with claws and a tube-shaped mouth - that live in moss, gutters, glaciers, and abyssal trenches. The space experiment, called TARDIS, was the first to expose an animal directly to open space. Most survived the vacuum. A smaller group survived both vacuum *and* the full spectrum of unfiltered solar radiation. Several of the females laid viable eggs after coming back down.

Their trick is called *cryptobiosis*. Faced with desiccation, cold, heat, or radiation, a tardigrade expels almost all the water from its body, curls into a barrel-shaped *tun*, and replaces its lost water with specialized proteins that turn the inside of its cells into a glass-like solid. Metabolism stops. Damage stops. The animal is not dead; it is paused. Add a drop of water and it resumes within hours.

Tardigrades have been revived from samples stored more than thirty years, baked at 150 °C, frozen near absolute zero, and squeezed at pressures six times those of the deepest ocean. Of every mass extinction Earth has suffered, they have walked through all five.

If anything on this planet outlasts us, the smart money is on the water bear.