More than 60 moons orbit Jupiter. One of these moons is Europa. It is especially intriguing to scientists. Miles below its cracked icy surface lies a deep saltwater ocean. Future missions to Europa will investigate these oceans for signs of life. If life exists, what kinds of organisms could survive in such a cold, dark place? To answer this question, scientists look to some of the most extreme environments on Earth.

Image credits: main image, NASA.