Close to midnight on February 15, 1977, a remotely operated still-camera sled that was photographing the floor of a mid-ocean ridge northeast of the Galápagos Islands recorded an unusual spike in the temperature of the otherwise freezing waters. The team of scientists controlling the camera sled from a nearby research vessel initially wrote off the reading as an anomaly. But hours later, when they reviewed the hundreds of photos snapped by the camera, they saw that in the few seconds corresponding to the temperature spike, the sea floor had morphed from a barren volcanic landscape into a dense and thriving agglomeration of clams and mussels. On February 17, a three-person team plunged 8,000 feet below the ocean’s surface in a research submersible to investigate that very spot. They found an oasis of misty-blue, 46°F waters, shimmering with manganese and other mineral precipitates. But that wasn’t all they saw.

Plate tectonics theory, which was finally accepted by the scientific community in the 1950s and ’60s, had predicted the existence of hydrothermal vents—deep-sea hot springs that form when cold seawater seeps into magma-emitting cracks on the ocean floor, heats up, and rises. Although geologists and marine scientists had been actively searching for vents since the early 1960s, it was the 1977 Galápagos Hydrothermal Expedition, led by Richard Von Herzen and Robert Ballard of the Woods Hole Oceanographic Institution, that confirmed their existence.

There were no biologists on the original expedition because no one had expected to find life thriving in the perpetual darkness of the ocean depths. As a result, the crew was not equipped to preserve the vast collection of strange organisms they encountered during their dives into the Galápagos Rift. They resorted to using Russian vodka as a preservative in place of formaldehyde. In 1979, however, a team of biologists led by marine scientist J. Frederick Grassle, then at Woods Hole, returned to the volcanic vents to study their unique ecosystems. They turned up a wealth of organisms completely new to science—from blind crabs to giant clams and mouthless tubeworms.

In what has been hailed as one of the greatest discoveries of the 20th century, Grassle and the biologists who studied the vents’ denizens found that the deep-sea ecosystems were powered not by the energy of the sun, but by chemicals being spewed from deep within the Earth’s crust. Specifically, bacterial communities living near the vents were harnessing the potential energy of the chemical bonds of hydrogen sulfide and other sulfur compounds emitted from the vents to synthesize glucose from water and dissolved carbon dioxide—a process known as chemosynthesis.

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