Subglacial Lake Mercer, is a hydraulically active lake lying 1,067-meters (3,500 feet) below the Whillans Ice Plain, a fast-moving section of the West Antarctic Ice Sheet. Lake Mercer covers 166 square kilometers (62 square miles), twice the size of Manhattan.
The lake is estimated to be 10 to 15 meters (33 to 49 feet) deep. Even with temperatures that stay below 0 °C, the lake doesn’t freeze, because of the intense pressure from the ice above.
Until now, scientists have only seen the lake “indirectly,” using ice-penetrating radar and other remote-sensing techniques, according to the press release by the scientific journal Nature.
The SALSA researchers used a hot-water drill to bore through a kilometer of ice, creating a portal with a diameter of just 60 centimeters (26.6 inches). On December 26, researchers funded by the US National Science Foundation (NSF) succeeded in melting the portal to what would lie below the ice.
Tiny carcasses of ancient life
While cleaning lake mud off an instrument they had been using to measure the lake’s water temperature, the scientists decided to take a look at the mud under a microscope. The scientists saw diatoms and photosynthetic algae that lived and died millions of years ago. But something else was discovered, and this was surprising, reports CTV News Canada.
David Harwood, a micro-paleontologist at the University of Nebraska-Lincoln who is part of the expedition, said he spotted the shell of a shrimp-like crustacean, a tiny invertebrate called tardigrade (or water-bear) with legs still attached. Its carapace was speckled and discolored “like an old leaf that’s been sitting on the ground for a season.”
Then, Harwood found another shell fragment of the shrimp-like creature, this one a healthy amber hue, and still bristling with delicate hairs. ”It looked really fresh,” he says. “Like something that had been living.” Harwood wondered – Could these animals still be living so far below, sealed off from the outside world?
According to the authors of the Nature paper, samples of the lake’s water contained enough oxygen to support aquatic animals and were full of bacteria — at least 10,000 cells per milliliter. But this raised the question of how sea creatures could survive in a freshwater lake.
The theory is that the creatures probably inhabited ponds and streams in the nearby Transantarctic Mountains, which pass 50 kilometers south of Lake Mercer and may have washed into the lake during brief warm periods when the glaciers receded. These warming periods also allowed seawater to intrude under floating ice and reach the lake.
John Priscu, a lake ecologist at Montana State University in Bozeman and the SALSA project’s leader, was cautious but excited about the discovery of the water-bear fragments, He is worried that the fragments his team found in the lake might simply be contamination carried in by dirty equipment.
“I’m pretty cautious about making claims,” he said — while allowing that discovering animals alive in Lake Mercer “would be a real wow moment” if it happened. The team, taking this into consideration, thoroughly re-cleaned all the equipment and tried again – and continued to find crustacean shells and other organisms.
The team plans on carbon-dating the fragments to determine more precisely how long ago they lived, as well as attempt to sequence their DNA. But this discovery has broader implications for science. Gizmodo points out that with the discovery of ice-covered water on Jupiter’s moon Europa and deep beneath the Martian polar ice caps, finding organisms under Antarctica’s ice gives us hope in finding life of other planets.
