James Bradley in The Guardian: The first hydrothermal vent was found in 1977 by scientists surveying the seabed 2,500 metres below the ocean on the Galápagos Rift, between Ecuador and the Galápagos Islands, who detected a temperature spike near the ocean floor. When the scientists reviewed the photos their submersible had taken, they were amazed to find a thriving community of living creatures. In an article published soon afterwards, the scientist Robert Ballard marvelled that the photograph taken just seconds before the temperature anomaly showed only barren, fresh-looking lava terrain. But for “13 frames (the length of the anomaly), the lava flow was covered with hundreds of white clams and brown mussel shells. This dense accumulation, never seen before in the deep sea, quickly appeared through a cloud of misty blue water and then disappeared from view. For the remaining 1,500 pictures, the bottom was once again barren of life.”
Since that first discovery, more than 600 fields of vents have been identified, all teeming with living organisms. Specially adapted colonies of mussels and other shellfish cling to their seething columns alongside fields of feathery worms and starfish; crabs and shrimp dart here and there, feeding in the cloudy water. Such richness of life should be impossible in the darkness of the ocean’s depths – without sunlight there is no photosynthesis. But the creatures that thrive around the vents do not draw upon the sun’s energy. Instead, they rely on chemosynthetic microbes capable of transforming the chemicals produced by the vents into energy.
The discovery of animals around hydrothermal vents has led to a dramatic broadening of our understanding of the sorts of environments in which life can survive. This has significant implications for the search for extraterrestrial life – if life thrives in such environments on Earth, it is plausible it might flourish in similar conditions in the oceans of ice moons such as Enceladus, which orbits Saturn. It has also shifted assumptions about where life on Earth began: perhaps it was not in a shallow pool, but somewhere in the depths of the primordial sea. In other words, the deep ocean might not be a place of death and forgetting, but rather the birthplace of life on our planet.
More here.
