Tardigrades can survive the most extreme conditions:

  • Heat of up to 151° C and cold of almost 0° K
  • Low pressure of a complete vacuum and high pressure of up to 1200 ATM
  • 10 years without water
  • 5000 Gy of radiation (5-10 is lethal for humans) and supposedly many environmental toxins

They took them to a low earth orbit and exposed them to open space for 10 days. More than two thirds of the animals survived and reproduced normally. Fascinating.