The animal that survived the vacuum of space

There is an animal half a millimetre long that can survive almost anything: freezing close to absolute zero, total dehydration for years, and doses of radiation that would kill just about anything else.

They are the tardigrades, or «water bears». When their surroundings become impossible, they dry out, shrink and enter a state in which they practically cease to exist. In 2007 they were sent into space and exposed to the vacuum and to direct solar radiation. Many came back to life once rehydrated.

They have been on Earth for more than 500 million years. They will probably outlive us.