Although they can survive unprotected in outer space, these resilient creatures are terrestrial living beings, not aliens as some have claimed. They are found on every continent on planet Earth and they love the water, yet can be found in the desert as well.
First discovered by pastor and zoologist Johann Goeze in 1773 and later named Tardigrada (Italian for "slow stepper"), these creatures still fascinate scientists today.
It's unlikely that Goeze knew how amazing tardigrades (also called water bears) really are. They can withstand a high temperature of 300 degrees and a low of -458 degrees F. They have also survived outer space, radiation, and six times the pressure of the deep sea.
How do they do this? When faced with adverse conditions they can desiccate - dry up - themselves. When in this state they are referred to as 'tuns' and resemble a little ball. It is a death-like state called cryptobiosis. Water bears usually only live a few weeks or months but can be revived from a state of cryptobiosis after 30 years.
Water bears need at least a small film of water to be in their normal mobile state. They suck water from the moss and plant matter they usually live in. They prefer living in the moist sediment in the bottom of lakes but have been found in arid regions as well. As long as there is just a little water, they can thrive.
Even though human beings might not survive a catastrophe such as a supernova or asteroids, it seems that water bears will be around many millennia after we are gone.
Alina Bradford, Tardigrade Facts, livescience.com
William Herkewitz, Secrets of the Water Bear, popularmechanics.com