The habitat involving microbes living inside rocks in extreme environments such as Antarctica’s Dry Valleys is the endolithic habitat.
“Endolith” means an organism that lives within rock, mineral, coral, shells, or the pores between mineral grains. Endolithic communities can include bacteria, archaea, fungi, algae, lichens, and amoebas. Rock provides shelter from intense ultraviolet radiation, wind, temperature swings, and drying.
Antarctica’s McMurdo Dry Valleys contain some of the best-known examples. There, cold-adapted microbes occupy tiny cracks and pores where a little moisture and protection from the harsh surface climate are available. Some can use photosynthesis, while others obtain energy through chemical processes involving minerals such as iron or sulfur.
A common mix-up is “hypolith.” Hypolithic organisms live beneath translucent rocks, whereas endoliths live inside the rock itself. “Cryptoendolith” is narrower still: it describes organisms occupying hidden internal cavities and pore spaces. Endolithic life is also important to astrobiologists because protected rock interiors are considered possible refuges for microbial life on Mars.