Virtually all biology textbooks insist that all terrestrial life ultimately depends upon sunlight for its survival. In fact, the domain of chemosynthetic life has now been extended to a Romanian cave that has apparently been almost completely sealed off from surface influences for 5.5 million years.
Air does leak in through tiny cracks, and water partially fills the cave.
The roster includes isopods, a millipede, a centipede, a water scorpion, and a leech. Of course, bacteria and fungi thrive there, too. In contrast to unsealed caves, where insects, bats, and other sources of food filter in from the surface, life in the Romanian cave seems to derive entirely from hydrogen sulfide present in the cave's rocks. This compound is consumed by microorganisms, which are then grazed by cave occupants higher up the food chain. And indeed it might be, for Mars has plenty of rocks and subsurface water.