Science journalist Douglas Fox is in Antarctica on assignment for DISCOVER Magazine as the WISSARD Embedded Journalist.
The search continues for life in subglacial Lake Whillans, 2,600 feet below the surface of the West Antarctic Ice Sheet—but a thrilling preliminary result has detected signs of life.
At 6:20am on January 28, four people in sterile white Tyvek suits tended to a winch winding cable onto the drill platform. One person knocked frost off the cable as it emerged from the ice borehole a few feet below. The object of their attention finally rose into sight: a gray plastic vessel, as long as a baseball bat, filled with water from Lake Whillans, half a mile below.
The bottle was hurried into a 40-foot cargo container outfitted as a laboratory on skis. Some of the lake water was squirted into bottles of media in order to grow whatever microbes might inhabit the lake. Those cultures could require weeks to produce results. But one test has already produced an interesting preliminary finding. When lake water was viewed under a microscope, cells were seen: their tiny bodies glowed green in response to DNA-sensitive dye. It was the first evidence of life in an Antarctic subglacial lake.
(A Russian team has reported that two types of bacteria were found in water from subglacial Lake Vostok, but DNA sequences matched those of bacteria that are known to live inside kerosene—causing the scientists to conclude that those bacteria came from kerosene drilling fluid used to bore the hole, and not from Lake Vostok itself.)
In order to conclusively demonstrate that Lake Whillans harbors life, the researchers will need to complete more time-consuming experiments showing that the cells actually grow—since dead cells can sometimes show up under a microscope with DNA-sensitive staining. And weeks or months will pass before it is known whether these cells represent known types of microbes, or something never seen before. But a couple of things seem likely. Most of those microbes probably subsist by chewing on rocks. And despite being sealed beneath 2,600 feet of ice, they probably have a steady supply of oxygen.
The oxygen comes from water melting off the base of the ice sheet—maybe a few penny thicknesses of ice per year. “When you melt ice, you’re liberating the air bubbles [trapped in that ice],” says Mark Skidmore, a geomicrobiologist at Montana State University who is part of the Whillans drilling, or WISSARD, project. “That’s 20 percent oxygen,” he says. “It’s being supplied to the bed of the glacier.”
In one possible scenario, lake bacteria could live on commonly occurring pyrite minerals that contain iron and sulfur. The bacteria would obtain energy by using oxygen to essentially “burn” that iron and sulfur (analogous to the way that animals use oxygen to slowly burn sugars and fats). Small amounts of sulfuric acid would seep out as a byproduct; that acid would attack other minerals in the sands and sediments of the lake—leaching out sodium, potassium, calcium, and other materials that would accumulate in the water.
This process, called weathering, breaks down billions of tons of minerals across the Earth’s surface each year. Researchers working on the National Science Foundation-funded WISSARD project hope to learn whether something like this also happens under the massive ice sheets covering Antarctica and Greenland. They’ve already seen one tantalizing sign.
The half mile of glacial ice sitting atop Lake Whillans is quite pure—derived from snow that fell onto Antarctica thousands of years ago. It contains only one-hundredth the level of dissolved minerals that are seen in a clear mountain creek, or in tap water from a typical city. But a sensor lowered down the borehole this week showed that dissolved minerals were far more abundant in the lake itself. “The fact that we see high concentrations is suggestive that there’s some interesting water-rock-microbe interaction that’s going on,” says Andrew Mitchell, a microbial geochemist from Aberystwyth University in the UK who is working this month at Lake Whillans.
Microbes, in other words, might well be munching on minerals under the ice sheet. The Whillans team will take months or years to unravel this picture. They will perform experiments to see whether microbes taken from the lake metabolize iron, sulfur, or other components of minerals. And they will analyze the DNA of those microbes to see whether they’re related to rock-chewing bacteria that are already known to science.
Antarctica isn’t the only place in the solar system where water sits concealed in the dark beneath thick ice. Europa and Enceladus (moons of Jupiter and Saturn, respectively) are also thought to harbor oceans of liquid water. What is learned at Lake Whillans could shed light on how best to look for life in these other places.