Life in the Dark - Deep Sea Ecosystems

Deep-sea bacteria form the base of a varied food chain that includes shrimp, tubeworms, clams, fish, crabs, and octopi. All of these animals must be adapted to endure the extreme environment of the vents -- complete darkness; water temperatures ranging from 2°C (in ambient seawater) to about 400°C (at the vent openings); pressures hundreds of times that at sea level; and high concentrations of sulphides and other noxious chemicals.

Images courtesy Woods Hole Oceanographic Institution A variety of animals live near these hydrothermal vents, including the shrimps, crab, and anemone in this picture taken at the Indian Ocean vent. So far, the hallmark red and white tubeworms have not been spotted at this vent.

The ability of life to tap such geothermal energy raises interesting possibilities for other worlds like Jupiter's moon Europa, which probably harbour liquid water beneath its icy surface. Europa is squeezed and stretched by gravitational forces from Jupiter and the other Galilean satellites. Tidal friction heats the interior of Europa possibly enough to maintain the solar system's biggest ocean. Could similar hydrothermal vents in Europa's dark seas fuel vent ecosystems like those found on Earth? The only way to know is to go there and check.

Astrobiologists are increasingly convinced that life on Earth itself might have started in the sulphurous cauldron around hydrothermal vents. Vent environments minimise oxygen and radiation, which can damage primitive molecules. Indeed, many of the primordial molecules needed to jump-start life could have formed in the subsurface from the interaction of rock and circulating hot water driven by hydrothermal systems.

If this idea proves true, then the next time Van Dover gazes through the submarine's camera at the vents on the floor of the Indian Ocean, she may be seeing both a portrait of life's genesis in Earth's distant past - and a glimpse of alien life yet to be discovered.