Tardigrades are 500 million years old and at first glance, very intimidating. They have podgy faces, eight legs, ferocious claws and dagger-like teeth. They are never more than 1.5 mm long and can only be seen with a microscope. They have been discovered up a mountain in the Himalayas, in Japanese hot springs, at the bottom of the ocean or even in Antarctica.
- In 1964, scientists exposed Tardigrades to lethal doses of X-rays, alpha, gamma and ultraviolet radiation and found that they could survive. In 2007, radiation was one of the biggest threats facing the Tardigrades when they were attached to a satellite and blasted into space. After the satellite had returned to Earth, scientists found that many of them had survived. Some of the females had even laid eggs in space and the newly-hatched young were healthy.
- Tardigrades can tolerate being frozen to -272.8 °C, just above absolute zero. To put that into perspective, the lowest temperature ever recorded on Earth was a balmy -89.2 °C in central Antarctica. They coped with a profound chill that does not occur naturally and must be created in the lab, at which atoms come to a virtual standstill.
- In 1842 a French scientist showed that a Tardigrade could survive being heated to temperatures of 125 °C for several minutes; in 1920 a Benedictine friar brought Tardigrades back to life after heating them to 151 °C for 15 minutes.
- In 1998, a study found that Tardigrades could survive a pressure of 600 MPa. This is beyond anything they might encounter in nature: the deepest part of the sea is in the Mariana Trench, which goes down 10,994 m and the water pressure is around 100 MPa.
- And finally, when a Tardigrade dries out, it enters a deep state of suspended animation that closely resembles death and its metabolism slows to 0.01% of the normal rate. It can stay in this state for decades, only reanimating when it comes into contact with water.
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