Presently the surface of Mars is very dry and any liquid water that reaches it quickly boils away since the martian atmospheric pressure is what you could experience in your space suit 30 to 50 miles above the Earth's surface. However, since the martian gravity is about 1/3 that of the Earth, it's crust is less dense and more porous than what we find on our home planet. This situation leads Dr. Alfred McEwen of the University of Arizona's Lunar and Planetary Laboratory to state “I consider it likely that there are deep pockets of water in the martian crust not yet detected”. Letting our imaginations run wild, if there are deposits of liquid water miles underground perhaps there might be subterranean lakes fed by volcanic tubes. Lava tube environments could be warmed by geothermal sources, have trapped, enclosed, pockets of liquid water, and be replenished by water flows up from the martian mantle. Even today these deep martian caves are theoretically likely to contain warm mineral rich liquid water in contact with a thermal energy source. It is intriguing to consider that deep inside Mars all of the necessary ingredients for life may be present together. On Earth we find this type of environment near hydrothermal vents on the ocean floor to have rich biological diversity of living organisms. Perhaps there are martian organisms in deep underground aquifers that migrated there from the surface as conditions changed or maybe that has always been their home. The only way to know if any parts of this fantasy are true is to find and explore the deep caves of Mars.