Title:
Habitability on ocean worlds tied to composition and orbital-thermal evolution

Abstract:
Composition and orbital-thermal evolution are key to understanding the past and present habitability of ocean worlds in our solar system. The bulk composition determines whether the ingredients necessary for life to exist may be available. The orbital-thermal evolution of the ocean world determines the temporal and spatial distribution of the ingredients. Which ocean worlds are more habitable for life as we know it?

Using thermodynamic phase relations and Gibbs free energy minimization, I will show a model to identify and quantify the reactions caused by thermal excursions, and the organic molecule and hydrocarbon species (methane, ethane, lactate, glutarate, etc.) in fluids produced in (and released from) the interiors of different ocean worlds. Water-rock interactions lead to end products (organic molecules, redox-sensitive species, minerals) that are fundamentally different between ocean worlds with different orbital-thermal histories, notably between ocean worlds that are probably differentiated (e.g. Europa) and those that are probably not (e.g. Titan, Enceladus). Worlds that are currently warmed are probably more habitable today, but worlds that experienced high temperatures in the distant past were probably habitable when life arose on Earth.