Planetary water-rock interfaces generate energy in the form of redox, pH, and thermal gradients, particularly in hydrothermal systems where the reducing, heated vent fluid feeds back into the more oxidizing ocean. Alkaline vents produced by serpentinization have been proposed as a possible location for the emergence of life on the early Earth due to various factors, including the mineral precipitates that resemble inorganic catalysts in enzymes and the presence of electron donors and acceptors in hydrothermal systems (e.g. H2 + CH4 and CO2) that may have been utilized in the earliest metabolisms.
Many of the factors prompting interest in alkaline hydrothermal vents on Earth may also have been present on early Mars, or even presently within icy worlds such as Europa or Enceladus. Of particular importance for possible proto-metabolic reactions in alkaline hydrothermal systems are mineral chimneys that precipitate at the vent fluid / seawater interface. Hydrothermal chimneys are an example of geological chemical gardens – a self-organizing non-equilibrium process that forms complex structures fueled by steep concentration gradients across the reaction-precipitation zone. Chemical garden and inorganic membrane systems have many properties of interest to the origin of life that can be simulated in the laboratory, for example: they can precipitate metastable catalytic mineral phases; the chemical garden structure can act as a flow-through chemical reactor and concentrator; and they can even generate electrical energy from the trans-membrane gradients and drive redox reactions.
In this talk I will give an overview of how we use chemical gardens to simulate far-from-equilibrium geochemical systems such as vents, and future directions for using electrochemical / fuel cell techniques to characterize prebiotic potential and habitability in seafloor systems.