PREDICTING HYDROTHERMAL FLUID COMPOSITIONS AND CONSEQUENCES OF WATER-ROCK-ORGANIC-MICROBIAL REACTIONS (Invited Presentation)

Hydrothermal fluids react with everything in their path. Modeling the consequences means including all of the minerals, gases, inorganic solutes, organic compounds and biomolecules that hydrothermal fluids can transform. We focus on expanding the capacity to include aqueous solutes, organic compounds, and biomarkers in theoretical models of hydrothermal systems, while using the results to explore the generation of equilibria and disequilibria during submarine and continental alteration on Earth and the other ocean worlds of the solar system. Recent advances with estimation methods make it possible to include thousands of aqueous metal-ligand complexes in speciation calculations and permit us to explore changes in speciation of metals and organic compounds throughout geochemical and biological fluids. Predicting solute transport depends in part on evaluating speciation as temperature, pressure, and composition change, so it follows that enhanced data for aqueous species permit new perspectives on water-rock-organic reactions during weathering, hydrothermal alteration, and subduction processes. Likewise, current capabilities to conduct thousands of mass-transfer calculations rapidly makes it possible to test wide-ranging hypotheses by generating massive forward-modeling libraries. The results can be mined for multidimensional combinations of temperature, pressure, composition, and extent of reaction that correspond to observations from natural systems. Increasingly, mechanistic understanding of organic reactions allows use of organic compound ratios as tracers for temperature, pH, and redox states of otherwise inaccessible subsurface conditions, and as clocks for the duration of geochemical processes. At lower temperature populated portions of hydrothermal systems, we are finding that biomolecules from bulk microbiome samples track geochemical conditions and thermodynamic states. These observations lead to hypotheses that hydrothermal microbes cannot escape the stoichiometry of their metabolisms, and that biomolecules have to function as cheaply as possible.