Frigid lakes locked beneath the Antarctic ice sheet may be home to more microbial life than scientists ever imagined.

More than 400 subglacial lakes lie beneath the Antarctic ice sheet, completely shut off from sunlight, according to the new paper, published Feb. 17 in the journal Science Advances. These lakes form where the weight of the surface ice bears down on the base of the sheet, generating intense pressure and lowering the melting point of the ice. As the base melts, the remaining ice insulates the meltwater from cold air, while geothermal heat from the bedrock below also helps prevent freezing, according to a statement.