Microbial life can exist in the most extreme environments on Earth. In a recent study, researchers reported the first direct evidence of life in a lake located almost a kilometre below an ice sheet in Antarctica. The ice provides an effective "duvet," trapping the heat naturally emitted through the Earth's crust. There is growing evidence that many of the Antarctic lakes are connected by a network of channels. These channels control the flow of overlying ice streams, and liquid water at the base of ice sheets lubricates the passage of ice. The lakes associated with ice streams are thought to act as reservoirs for this process, filling and partly emptying on a fairly regular basis, so the water in the lake is replaced every few years. Glacier Lake Chileans, described in the study, is an example of a dynamic glacier lake. It receives no light to support photosynthesis, has constantly low temperatures (just a little below zero) and is under pressure eighty times atmospheric pressure due to the 800m of overlying ice With relatively frequent changing of the lake water, the availability of organic matter, which humans and many other life forms collectively termed heterotrophs use for energy and growth, will be limited. The only things that can support the heterotrophs in this ecosystem are the underlying ancient seabed geology, which can provide small amounts of organic carbon from the material, and the recycling of carbon from dead microbes.