This is Part 1 of a 6-part series that tells the story of humankind’s efforts to understand the origins of life by looking for it in extreme environments where life survives without relying on energy from the Sun. By understanding how life can survive without the Sun, we may discover how life began on our planet, and whether or not Earth is the only place in the universe capable of supporting a biosphere.

It was in 1977 that scientists used the Alvin submersible to collect water samples from the seafloor and were greeted with the horrible stench of rotten eggs. The discovery of hydrogen sulfide deep below the ocean was a watershed moment in humankind’s understanding of the origins of life, and came just as the Voyager 2 spacecraft was providing the first clues of a possible ocean on Jupiter’s moon Europa.

In 2012, Chris German of the Woods Hole Oceanographic Institution led an oceanographic expedition to the Mid-Cayman Rise. They studied new hydrothermal vent sites that he and his colleagues had explored during two prior survey expeditions in 2009 and 2011. By studying the life that thrives at hydrothermal vents, astrobiologists are gaining a better understanding of life’s potential deep below the oceans of other worlds in our solar system and beyond.