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Extremophiles challenge everything we thought we knew about the existence of life on Earth. Now, astrobiologists are questioning if some extremophiles are actually aliens living among us. Just who are these incredible creatures, and what can we learn from them?
Extremophiles are organisms that thrive in the most extreme environments on Earth. From the sulphuric hot springs in Yellowstone National Park to the icy Antarctic, these creatures push the limits of what we know about biology, and force us to reevaluate the possibility of extraterrestrial life forms. Scientists are finding an ever-increasing number of these tough little organisms living quite happily in places where we previously believed no life could possibly exist. Extremophiles have even been found nestled in the heart of a nuclear reactor.
The Chernobyl fungus was discovered several years ago, when scientists were using an R.O.V. to inspect the Chernobyl site. To their surprise, they found a dark slime on the walls, living within the reactor and actually feeding on the radiation. The melanin-rich fungus increases rapidly in size when exposed to a high level of gamma rays (and no, you wouldn't like it when it's angry). Other fungi and bacteria have been discovered with the same ability to thrive within radioactive environments. Deinococcus radiodurans, an amazing polyextremophile with the distinction of being considered the world's most durable bacterium, is capable of withstanding 5,000 Grays of radiation (500,000 rads). The discovery of such fungi and bacteria have provided scientists with a dramatic breakthrough in finding organic ways in which to detoxify radioactive waste.
Extremophiles are not just microbes; more highly evolved creatures have also proved to be as durable, and as strange and wonderful, as the Deinococcus radiodurans bacteria.
The Pompeii Worm
This extremophile keeps a cool head even in extreme temperatures. The Pompeii Worm finds a habitat on or near Black Smokers, hydrothermal vents on the sea floor, which give the worm its volcanic name. Nestled within its cozy tube, its body stays at a very toasty 175º F, while its plume-like head protrudes from the tube into water that is a much more temperate 72º F. Weirder still, its fleecy coat is actually a colony of bacteria that lives in a symbiotic relationship with the worm, fed by mucus secretions produced by the worm. Truly an oddity, the Pompeii worm (and its living coat) obviously has a lot to teach us about living in an extreme range of temperatures.
The Tardigrade 
The Tardigrade is considered the king of the extremophiles. These microscopic organisms look like clear gummi bears come to life (hence their more common name, "Water Bears") and have proven to be more durable than Twinkies. Tardigrades have been discovered all over the world, and in the most amazing places, from the peaks of the Himalayas to the sea floor, from temperatures approaching absolute zero to temperatures over 303° F. 
Like the Chernobyl fungus, these wonderful Water Bears can withstand doses of gamma rays lethal to humans without flinching. Tardigrades can also withstand the extreme pressure of a vacuum, and research is being conducted to test Tardigrades' durability in space. The Tardigrade Space program has been geekily nicknamed... yes, you guessed it... TARDIS.
NASA astrobiologist Richard Hoover is leading the hunt for more extremophiles, hoping to prove that some of these little fellas are not of our world, but interstellar hitch-hikers that came here millions of years ago on meteors. The existence of organisms like Deinococcus radiodurans and the Tardigrades gives weight to the argument that some of these extremophile lifeforms are actually aliens among us. If these creatures can exist in the vacuum of space and withstand such high levels of radiation, then it is just possible that these abilities are evolutionary traits that enabled them to arrive here, on Earth, from somewhere else in the galaxy.
The Extremophile Hunter:
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