Diverse geochemical conditions for prebiotic chemistry in shallow-sea alkaline hydrothermal vents

Hydrothermal systems, where geothermally heated water discharges through a planet’s crust, occur on land or underwater. Hydrothermal systems have been proposed as environments that could support the emergence of life, with particular attention given to deep-sea vents and on-land hot springs. We propose that alkaline hydrothermal vents in shallow waters (<200 m depth), high-energy environments that display diverse and variable geochemistry, should also be considered in origin-of-life scenarios for the early Earth. Two active alkaline shallow vents—the Strytan Hydrothermal Field in Iceland and the Prony Hydrothermal Field in New Caledonia—provide examples of the conditions found in shallow-sea vents that may be relevant for facilitating prebiotic chemical reactions. These conditions include wet–dry cycling, temperature variations, and influxes of both saltwater and freshwater. We argue that the spatial and temporal geochemical variability in shallow-vent hydrothermal systems can support a range of prebiotic chemical reactions required for the emergence of life.