... in 1977, when oceanographers working deep in the Pacific found bizarre ecosystems lush with clams, mussels and long tube worms.
When brought to the surface, the creatures smelled of rotten eggs, a sign of sulfur. It turned out that the ecosystem's main energy source was sulfur compounds emitted by the hot vents, in particular hydrogen sulfide. The primary producers (like plants on land) were tiny microbes thriving on volcanic heats and chemical energies rising from the earth's interior.
The dark ecosystems forced scientists to conclude that not all life on earth depends on the sun's energy or on photosynthesis.
As similar communities were found in the deep, intrigued scientists theorized that the vents were perhaps windows on a deep microbial world, a hidden biosphere extending for miles into the earth's crust, with a total mass rivaling or exceeding that of all surface life. Even stranger, they suggested that life on earth might have begun in such realms, nurtured by a steady diet of hot chemicals.
Since those frenetic early days, ocean scientists have found not only scores of such deep oases but strong evidence that they do in fact represent the tip of a very old, very large ecosystem.
It appears that the most primitive of these organisms, and perhaps the most common, metabolize iron. Next we'll learn that oil is a waste byroduct of the metabolism of a bizarre crustal organism. We live on an increasingly weird world in an increasingly weird universe.