Cryopeg
Cryopegs are lenses of perennially overcooled water brines or a layer of unfrozen ground that is permanently cryotic (forming part of the permafrost), but freezing is prevented by freezing-point depression due to the dissolved-solids content or the pore water.
Cryopegs make up the only habitat on Earth that is characterized by permanently subzero temperatures, high salinity, and isolation from the influence of external factors during geological time. Cryopegs are habitats for microorganisms, like bacteria.