Our basic premise is that life on Earth is the best model we have for life elsewhere. Study of life in extreme environments on Earth guides the search for extraterrestrial life. Temperature, Pressure, and Minerals Hydrothermal fluids venting from Earth's subsurface crust onto the deep seafloor meet the carbon, nitrogen, energy and other mineral requirements for life. The hypothesis that the upper temperature limit for life is extended significantly by fluid mineral content and hydrostatic pressure remains largely untested.
Vent systems are the perfect laboratory.
This means we must examine the extremes. We know little about survival strategies of extremophiles. In deep terrestrial basalt formations, microorganisms persist indefinitely without organic carbon from the surface. Physically, sea-ice varies from fine ice particles suspended in water to thick blocks of ice hundreds of meters across. Sea ice is colonized internally by many microorganisms.