FEHM source code modifications and executables for use with ocean-world gravity

This is a repository for compiled codes, source code, and input files used in this paper: Fisher, A. T., K. D. Dickerson, D. K. Blackman, N. Randolph-Flagg, C. R. German, and C. Sotin (2024), Sustained hydrothermal circulation under ocean-world gravity, J. Geophys. Res. - Planets, submitted and in review. Plain language summary from paper: Ocean worlds are planets, moons, and other rocky bodies that have a liquid ocean, often under an icy shell or within the rocky interior. In our solar system, ocean worlds include several moons of Jupiter and Saturn. Some of these ocean worlds are thought to have active hydrothermal circulation, where water, rocks, and heat combine to drive fluids in and out of the seafloor. Hydrothermal circulation could impact the chemistry of the water, rock, and ice of ocean worlds and provide chemical energy that allows life to develop deep below the icy surface. This study shows results from computer simulations of hydrothermal circulation, using a well-understood system on Earth as the basis for comparison to conditions on an ocean world that has much lower gravity (because it is smaller than Earth). The simulations show that fluid flow much like that occurring at seafloor sites on Earth could occur under ocean world gravity, but with several important differences. Lower gravity results in less buoyancy, where warmed fluid expands and becomes lighter than nearby cold fluid. Less buoyancy tends to reduce flow rates in a hydrothermal system, and this can result in higher temperatures of the circulating fluid, and more extensive chemical reactions. Lower gravity can also result in hydrothermal systems transporting less heat, and this could allow these systems to last longer on an ocean world.