If you want to find life on other worlds, then you may want to start by searching the deepest, most remote areas of our seafloor. At hydrothermal vents, high pressure and heat from volcanic activity transforms seawater into hot, mineral-laden water. These hot springs support thriving ecosystems that exist completely devoid of sunlight. Chemical clues in hydrothermal vent fluids reveal the presence of a subseafloor biosphere, and recent exploration in the Arctic uncovers the nature of hydrothermal venting below meter-thick ice at the top of the world.