NARRATOR Biologist Tim Shank explores the oceans here on Earth, that most resemble Europa's icy depths. Two hundred miles from the North Pole, Tim sends robots to search for life, 12,000 feet beneath the Arctic ice sheets, where the sunlight never reaches.

TIM SHANK (BIOLOGIST, WOODS HOLE OCEANOGRAPHIC INSTITUTION) Exploring the deep Arctic Ocean is not unlike exploring another planetary body in our solar system. You have to deal with immense pressures, temperatures, extremes where life might exist.

NARRATOR Here, volcanic activity is pushing apart the seafloor. Scientists believe that something similar may be at work under the ocean on Europa.

JIM GREEN (DIRECTOR, PLANETARY SCIENCE DIVISION, NASA) We believe it has a rocky core. That rocky core is under tidal forces and influences, and it's flexing also, just as the rest of the planet does. And that heat has to go somewhere.

NARRATOR On the restless floor of the Arctic Ocean, Tim's robots discover evidence of an extremely hostile environment. Volcanic vents are spewing out water that is super-heated to 700 degrees and laden with toxic chemicals like hydrogen sulfide.

Tim believes that vents like this could also exist on Europa's ocean floors. And, clustered around the vents, in pitch darkness, Tim's team finds life.

TIM SHANK We discovered new forms of life, microbes that cover miles of the sea floor there. There's life even in the, the coldest waters in the deepest regions of our polar oceans that we didn't know about before.

NARRATOR Instead of using sunlight to trigger vital reactions, microbes like these use sulfur, hydrogen and methane as chemical sources of energy. And the microbes form the basis of an extensive food chain.

The discovery of life here raises the possibility of life on Europa.

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