Boundary Layer Models of Martian Hydrothermal Systems

Many geomorphic features on the surface of Mars, such as gullies, fans, paleolakes, outflow channels, and deltas, were likely caused by flowing water; however, the source of that water is disputed. One possible water source is a hydrothermal system driven by a magma intrusion. We investigated such hydrothermal systems by first developing analytical, steady state, two-dimensional, thermal boundary layer models in order to determine the mass and heat fluxes near the quasi-vertical boundaries of magma intrusions with heights ranging from 1 to 10 km. We analyzed the effects of various permeabilities and intrusion dimensions on the heat and mass fluxes generated by hydrothermal flow. Results showed, for example, that a 100 km long dike with a depth of 5 km injected into a highly permeable rock would produce |sim 1019 J/yr of heat and transport ~ 10 km3/yr of fluid. This and additional mass flux results were compared with hydrographs estimating the volumes of fluid outflow and durations of flow needed to form various observed geomorphic features. The hydrograph comparisons indicate that flow from such hydrothermal systems could be responsible for some fluvial features on Mars including gullies and stepped fans. The relatively small flow volumes suggest it is unlikely that the larger features were formed directly by out flowing hydrothermal fluids. However, additional fluid may result from the melting of subsurface ice as a result of hydrothermal heat transport.