Bacteria on Earth can live five kilometers below the surface. They can live on nothing but rock and water, extracting energy from chemical reactions rather than sunlight. Life on Earth, and perhaps Mars and other planetary bodies, may have originated in such strange environs, and if so, the subsurface of water-rich planets, asteroids, and satellites might be home to a rich diversity of microorganisms.
In the dream, you are in an ice cave. It is starkly beautiful, suffused in blue light from an outside source. There's nothing to eat, no sustenance, just the angular planes of ice crystals. It is stunningly cold, well below freezing. Your breath billows in front of you; perspiration forms a frozen rind on your neck. You can't stay here long. Then you notice creatures working industriously along the far wall of the cave. They're oblivious to the intense cold. From the strange smell, you guess that they have antifreeze running through their veins. This place is clearly their home.
Then you awake—not to your bed but to another strange world. You are on the shores of a river, with canyon walls that rise up and disappear in the gloom. The river is acrid and filled with the worst kind of industrial effluent. The water is so acidic that it sizzles as it passes over the rocks, which are themselves discolored by chemical residue. The smell is foul and metallic, and it almost makes you gag.