Stunned researchers in Antarctica have discovered fish and other aquatic animals living in perpetual darkness and cold, beneath a roof of ice 740 meters thick. The animals inhabit a wedge of seawater only 10 meters deep, sealed between the ice above and a barren, rocky seafloor belowa location so remote and hostile the many scientists expected to find nothing but scant microbial life.
A team of ice drillers and scientists made the discovery after lowering a small, custom-built robot down a narrow hole they bored through the Ross Ice Shelf, a slab of glacial ice the size of France that hangs off the coastline of Antarctica and floats on the ocean. The remote water they tapped sits beneath the back corner of the floating shelf, where the shelf meets what would be the shore of Antarctica if all that ice were removed. The spot sits 850 kilometers from the outer edge of the ice shelf, the nearest place where the ocean is in contact with sunlight that allows tiny plankton to grow and sustain a food chain.
I’m surprised, says Ross Powell, a 63-year old glacial geologist from Northern Illinois University who co-led the expedition with two other scientists. Powell spoke with me via satellite phone from the remote location on the West Antarctic Ice Sheet, where 40 scientists, ice drillers and technicians were dropped by ski-mounted planes. I’ve worked in this area for my whole career, he saysstudying the underbellies where glaciers flow into oceans. You get the picture of these areas having very little food, being desolate, not supporting much life. The ecosystem has somehow managed to survive incredibly far from sunlight, the source of energy that drives most life on Earth. The discovery provides insight into what kind of complex but undiscovered life might inhabit the vast areas beneath Antarctica’s ice shelvescomprising more than a million square kilometers of unexplored seafloor.
The expedition, funded by the National Science Foundation, had ventured to this location to investigate the history and long-term stability of the Whillans Ice Stream, a major glacier that flows off the coast of Antarctica and feeds into the Ross Ice Shelf. The expedition began in December as tractors towed massive sleds holding more than 400 metric tons of fuel and equipment to a remote location 630 kilometers from the South Pole and 1,000 kilometers from the nearest permanent base.
In early January the team began an unprecedented effort to drill through the ice to reach a place called the grounding zoneessentially, a subglacial beach where the glacier transitions from resting on bedrock to floating on sea water as it oozes off the edge of the continent. A team of ice drillers from the University of Nebraska-Lincoln (U.N.L.) used a jet of hot water from the end of a Kevlar hose a kilometer long and as big around as an ankle to melt a hole through the ice into the seawater below.
Until now no one had ever directly observed the grounding zone of a major Antarctic glacier. And from the moment the hole was first opened on January 7 Pacific time, it appeared that this place didn’t hold much in the way of life.
A downward-facing video camera lowered through the borehole found a barren sea bottomrocky, like a lunar surface, Powell says. Even deep abyssal ocean floors three or four kilometers deep in the ocean usually show some signs of animal life: the tracks of crustaceans that have scuttled over the mud, or piles of mud that worms have ejected from their burrows. But the camera showed nothing of the sort. Cores of mud that the team gently plucked from the bottom also showed no signs that anything had ever burrowed through underneath. And seawater lifted from the bottom in bottles was found to be crystal clearsuggesting that the water was only sparsely populated with microbes, and certainly not enough of them for animals to graze and sustain themselves on.
The water’s so clearthere’s just not much food, says Trista Vick-Majors, on a separate satellite call. Vick-Majors is a PhD microbiology student from Montana State University, who handled samples of water lifted from the bottom. What’s more, sediments in the sea floor were packed with quartz, a mineral that holds little nutritional value for microbes. When mud is raised from the bottom of an ocean or lake, it is often possible to smell gases such as hydrogen sulfide that are produced by microbesyour nose is a great detector of microbial activity, says Alex Michaud, a microbiology PhD student also from Montana State who is working with the sediment samples. But I don’t smell anything.
The revelation that something larger lived down there in the dark came eight days after the hole was opened, on January 15 Pacific time.
The finding depended on a skinny, 1.5 meter-long robot called Deep-SCINI, with eyes made of reinforced, pressure-resistant sapphire crystal and a streamlined body of aluminum rods and high-tech, syntactic foam comprising millions of tiny, hollow glass beads.
2015 Scientific American, a Division of Nature America, Inc.