Lost City Hydrothermal Field

The Lost City Hydrothermal Field is a field of alkaline hydrothermal vents located on the Atlantis Massif near the Mid-Atlantic Ridge, discovered in 2000. It is the largest known field of its kind, hosting more than thirty active vent structures — the tallest rising some sixty meters above the seafloor — and it is the type locality for the alkaline vent chemistry that has become central to theories of the origin of life.

Unlike black smokers, which are driven by volcanic heat and produce acidic, metal-rich fluid, the Lost City vents are driven by serpentinization — the exothermic reaction of seawater with mantle rocks (peridotite) that produces hydrogen gas and alkaline fluid. The process requires no magma; the heat is chemical, and the fluid chemistry is determined by water-rock interaction at depths of several kilometers. This makes Lost City a model for abiotic hydrogen production on any planet or moon with ultramafic rock and liquid water — including Mars and Europa.

The chimneys at Lost City are composed of calcium carbonate and magnesium hydroxide (brucite), not metal sulfides. They are white, porous, and warm (40–90°C), with internal microstructures that concentrate organic molecules and support diverse microbial communities. The field demonstrates that alkaline vent chemistry is not merely a theoretical construct for abiogenesis but an observable, active geological process on Earth today.