Lake Mercer lies beneath more than a kilometre of Antarctic ice, yet its water and sediments support microbial life. The lake is part of a flowing subglacial water system, rather than a sealed pocket whose organisms have remained isolated for millions of years.
Sampling a lake beneath the ice
The Subglacial Antarctic Lakes Scientific Access project, or SALSA, used hot-water drilling to reach Lake Mercer. A sediment study published in 2023 describes the lake as a water cavity about 15 metres deep beneath 1,087 metres of ice.
The project’s Antarctica research record describes water arriving from beneath both the East and West Antarctic ice sheets. Filling and drainage in upstream lakes influence Mercer. Water, sediments and microbes can move through this wider system.
What the sediment communities reveal
In the 2023 study, researchers examined bacteria and archaea in a sediment core. Communities near the sediment surface were more abundant and diverse than those deeper down.
Many of the dominant groups were related to microbes able to gain energy by oxidising nitrogen, sulfur or iron compounds. Carbon measurements also pointed to a contribution from old marine organic matter. The findings describe several interacting sources of energy and carbon, rather than a community sustained solely by minerals.
Lake Whillans, sampled in 2013, provides another record of microbial life beneath the West Antarctic Ice Sheet. Comparing the lakes helps researchers examine how water flow and sediment chemistry shape these environments.
Why subglacial lakes interest astrobiologists
These lakes also inform research on icy moons in the solar system. NASA’s account of Lake Whillans research explains why dark water beneath ice offers useful comparisons with Europa and Enceladus. Conditions vary between lakes and moons, so an Earth ecosystem is an analogue, not evidence that either moon is inhabited.
