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Project Progress

Task 1. Thermodynamics of Hydrothermal Organic Reactions (Shock, Zolotov)

During the last year Shock and Zolotov modeled the potential for microbial metabolism on Europa. Thermodynamic calculations were used to examine the possibility that sulfate reduction might be a metabolic strategy allowed by the complex chemical processes thought to occur on Europa. The model employs a sulfate-bearing ocean, originating from quenched hydrothermal fluids generated during differentiation, which interacts with hydrogen (H₂) released by hydrothermal fluids. The resulting energy is on the order of a few kilojoules per kilogram of water and is limited either by low H₂ or sulfate concentrations. This process represents an irreplaceable source of energy early in the history of Europa, owing to the likely decline of hydrothermal processes that generate H₂. If sulfate reduction remains a viable strategy for Europa, a source of reductant(s) other than H₂ would be required, including organic compounds.

Task 2. Theoretical Analysis of the Energetic Landscape of Ecosystems (Shock)

Because hydrothermal systems are populated by the deepest-branching organisms in the universal phylogenetic tree, they are the oldest continuously inhabited ecosystems on Earth. There is a clear interest in juxtaposing the genetic diversity with the geochemical (energetic) diversity in such systems. If such a relationship can be established, the results may reveal how ecosystems originate and evolve.