Superman has got nothing on the mighty tardigrades. These tiny but almost indestructible invertebrates can endure the most extreme conditions on Earth - and even beyond.
Although these eight-legged super-bugs require moisture to survive - a drop of dew is sufficient - the roughly 1,000 known species thrive in almost every habitat, from the sea floor to mountaintops and from the poles to the equator.
How are tardigrade able to survive such harsh conditions that would kill other animals?
Their secret? When the going gets tough, tardigrades just give up. They retract their legs into their bone an into a tiaht up. They ree aeneir legs into their bodies, roll up into a tight ball called a 'tun' and enter a coma-like state. They replace body water with preservative compounds, exude a protective wax over their cuticle and switch off their metabolism. They are as good as dead - and this will save their lives.
Tardigrade tuns can survive almost anything: drought, toxic chemicals and even temperature swings from -273°C to 151°C.
When conditions improve, they resuscitate and start where they left off, even after a decade
Scientists probing these critters' limits have found that they can tolerate pressures six times as great as in the deep ocean. But the ultimate test was in 2007, when two species were sent into orbit, and exposed to the suffocating vacuum of space and enough radiation to fry humans to a crisp. One-third of the bugs returned to Earth alive, making the tardigrade the only animal to survive extraterrestrial conditions.
- A tardigrade enters a deathlike stupor following one of four triggers: low oxygen levels, drought, extreme cold and changes in osmotic pressure (eg high salinity).
- One tardigrade in a rehydrated sample of moss showed signs of life after 120 years - briefly. It managed a few twitches, before falling still and presumably dying.
- One of the two species sent into space had a 1 per cent survival rate; the other's was 68 per cent. Half of the survivors themselves died within hours, but about 10 per cent lived long enough to mate and lay eggs, which hatched normally.