Hydrothermal vent communities weren't discovered until 1977, well after the first landings on Mars. Scientists believed that the deep ocean was cold, dark, and inhospitable to life. But when scientists started studying the areas where hot mineral-heavy water wells up like an underwater geyer in tectonically active-regions (seafloor rifts), they were surprised to discover that deep-sea vents were home to thriving communities, full of life. There were lots of animals, a high biomass, and many were active. Without photosynthesis, where does the energy come from?