Lake Enigma – a permanently frozen lake, deep in the northern foothills of Antarctica’s Victoria Land – was thought to be solid ice from top to bottom.

But, according to a new study, the lake’s icy surface rests on liquid water – and that water is filled with bizarre microbial life.

The study is published in Communications Earth & Environment.

A team of researchers journeyed out to Lake Enigma on an Italian Antarctic expedition in the 2019-2020 summer, where they drilled through the ice cover.

“A massive body of unfrozen stratified oligotrophic [nutrient-poor] water covered by up to 11m of ice was discovered and sampled,” write the researchers.

This body of water, up to 12m deep, is thought to have come from the nearby Amorphous Glacier.

The team looked at the elements and molecules in the water, and sequenced the RNA to identify the bacteria and other microbes that might be lurking in the depths.

“Lake Enigma supports a phylogenetically diverse and high-biomass microbial ecosystem that stands unique among Antarctic perennially ice-covered lakes,” write the researchers in the paper.

Since the lake is covered by about 10m of ice, year-round, this microbial ecosystem has been isolated from the rest of the world.

“Perennially ice-covered freshwater ecosystems are hotspots of biodiversity in Antarctica’s polar deserts, providing a year-round oasis for microbial life,” write the researchers in the paper.

“It is clear that Lake Enigma contains distinct ice-associated, planktonic, and benthic microbial communities. The ice-sealed planktonic and benthic microbiota of Lake Enigma likely represent persistent legacy biota that arose from the lake’s ancient microbial ecosystem before the freeze-up.”