It is surely the stuff of science fiction: An extraordinary being arrives on Earth that can withstand a tortuous array of conditions: boiling, freezing, tremendous atmospheric pressure, near total dehydration, and exposure to massive amounts of ionizing radiation. While many joke that “cockroaches would be the only thing to survive an extreme global nuclear war”, in fact, cockroaches would not. These creatures would. They are also the only life form known to be able to survive the near vacuum of space for extended periods. (Note: humans can actually survive the near vacuum of space for about 90 seconds without long term damage, but we have nothing on this creature.) They can lie dormant for 10-100 years and then come back to life with a drop of water. When it comes to durability, nothing on Earth can match the very real “Water Bear”- a tiny creature the size of a grain of sand (averaging about a millimeter long) that is lauded as the toughest creature on planet Earth.
There are over 1000 known species of Water Bears (called such because when they walk, their gait loosely resembles plump little bears ambling along on eight legs). Also known as “tardigrades” (from the Latin “tardigradus” meaning ‘slow walker’), they thrive in the most extreme environments on every corner of the Earth- from the Equator to the Polar regions- forests, swamps, deserts, tundras, mountains, glaciers, hot springs- from the highest point on Earth along the Himalayan mountain range, to the deepest parts of the sea, tardigrades are there. Less excitingly, they can also be found in your backyard where you can usually find them in common moss, lichens and ferns, feeding on natural detritus in the undergrowth.
Although the scientific community has long known about tardigrades (since 1773), it is still somewhat of a mystery how they manage the amazing feat of cryptobiosis, that is, the ability to almost completely halt their metabolic processes, losing up to 97%-99% of their total moisture. When they then encounter water again, they reanimate, with the current record being 120 years to reanimation (though that particular creature simply moved a little and then died when reanimated. But when we go to spans such as 10 years, most tardigrades are able to fully reanimate with no problem.)
One of the keys to this hardy creature’s success seems to be the presence of a cellular sugar called trehalose which preserves the membranes that form their bodies. Although hardly the answer to human suspended animation, scientists are looking at trehalose as a viable way to preserve human eggs during freezing for later fertilization.
In any event, when tardigrades dry up, they become “tuns”, little capsules that are easily transported and dispersed over the Earth via the wind, the oceans, or in an animal’s gut. (Yes, they can sometimes survive there too.) Besides their dehydration abilities, these little creatures can also go without oxygen for a time and withstand temperatures ranging from well above water’s boiling point to nearly absolute zero. (They’ve been shown to be able to survive as low as 1 degree above absolute zero for several minutes.)
Not remarkable enough for you? Tardigrades can also survive as high as 5,000 grays or 500,000 rads of ionizing radiation, though above 100,000 rads does seem to make them sterile. For reference, humans die around a “mere” 1,000-2,000 rads and will suffer significant damage with much less.
In order to test some of the tardigrade’s amazing abilities, in 2007, the European Space Agency launched the FOTON-M3 spacecraft hurtling a capsule full of science experiments into the heavens. Its subjects included live tardigrades, who returned from space after orbiting Earth for 12 days, all the while being subjected to the near vacuum of space and the full spectra of deadly solar and cosmic radiation. How did the Water Bears hold up? No problem for a large percentage of them. About 68% of them were just fine and kept on amblin’ once back on Earth. For reference, besides surviving the near vacuum of space, some species of tardigrade can also withstand up to 6,000 times atmospheric pressure at sea level. This is about 6 times more pressure than at the deepest point in the ocean. I, for one, welcome our new tardigrade overlords.