Impact‐Related Hydrothermal Conditions in Complex Craters on Mars

Kurzfassung

Impact craters can be used to track water activity on Mars because their formation can expose subsurface material (hydrated pre-impact) as well as create an environment for water to leave a mineralogical signature of its presence (post-impact). This work uses the iSALE shock physics code to simulate impact-induced heating and bedrock displacement in complex impact craters on Mars. In conjunction with an updated global groundwater model for Mars, we determine how, and if impact-induced hydrothermal alteration can be distinguished from pre-impact alteration. We examine the effects of impactor size and speed, bedrock porosity, and bedrock thermal gradient on hydrothermal conditions within impact craters. Bedrock heating was used to define the levels of hydrothermal conditions that could form within a crater. Our simulation results suggest that: (a) the central uplift is unlikely to preserve pre-impact alteration products because of the level of heating it suffers during crater formation, and (b) impact-induced heating is not sufficient to create hydrothermal conditions within the excavated proximal ejecta, suggesting that any hydrothermal signatures within the ejecta blanket are associated with the pre-cratering geological processes. We used the groundwater model depths to constrain when pre-impact alteration could occur. Finally, we outlined how our thermal anomaly size and geometry measurements, groundwater depths, and excavation depths can be used to assess the overall probability that an observed hydrothermal alteration product was formed pre- or post-impact.