Sources of nutrients and energy for a deep biosphere on Mars

Hydrothermal vents appear to be the tip of the subsurface biosphere in the ocean crust. The primary prducers in this biosphere are prokaryotes that to lerate a wide variety of physical and chemical conditions and are versatile in their use of inorganic compounds to drive metabolism. A synthesis of ch emical and mineralogical data from Martian meteorites and measurements of t he Martian surface suggest that conditions similar to those that make life possible in Earth's oceanic crust, namely, water, carbon, nutrients, approp riate temperatures, and gradients in redox conditions, also occur within Ma rs. Chemolithoautotrophic microorganisms capable of living below the seaflo or on Earth would probably survive in some regions of the Martian subsurfac e.