An ecosystem in the dark
Beneath 800 meters (2,625 feet) of the West Antarctic Ice Sheet lies Subglacial Lake Whillans, a body of water completely cut off from the sun and atmosphere. First identified in 2007 from satellite data that showed the ice surface rising and falling, this shallow lake is only about 2 meters (6.5 feet) deep but covers an area of 60 square kilometers (23 square miles). Its water remains liquid at a temperature of -0.5 degrees Celsius (31.1°F) due to the immense pressure of the ice above.
In January 2013, the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project successfully drilled a clean borehole into the lake. Using a specialized hot-water drill designed to prevent contamination, scientists retrieved the first-ever clean samples from an Antarctic subglacial lake. Analysis of the water and sediment revealed a surprisingly dense and active microbial ecosystem. The water contained around 130,000 microbial cells per milliliter, a concentration not unlike what is found in some surface lakes. Inside this dark world, researchers identified nearly 4,000 distinct species of bacteria and archaea.
Life without the sun
The microorganisms of Lake Whillans survive through chemoautotrophy, a process of creating energy from chemical reactions rather than from sunlight. Instead of photosynthesis, these microbes "eat" minerals and chemicals found in the water and the ancient marine sediments on the lakebed. The primary energy source for this ecosystem comes from the oxidation of ammonium and methane. Other microbes derive energy by processing sulfur and iron compounds, which likely come from the fine "glacial flour"—rock pulverized by the slow grind of the ice sheet against the bedrock.
This discovery confirmed that life can flourish in one of Earth's most extreme environments. The ecosystem is a collection of dormant survivors but a functioning community where microbes are actively metabolizing, reproducing, and cycling nutrients. The energy and organic carbon present are sufficient to support a complex food web. The existence of this self-sustaining habitat, fueled by geologic energy sources, shows how life might persist in other sunless, icy environments, such as on Jupiter's moon Europa or Saturn's moon Enceladus.