Impact-induced hydrothermal systems are important targets for Mars exploration. Their existence is confirmed by remote observation, in situ investigation by Mars rovers, and the study of Martian meteorites. However, ground truth is lacking for the alteration behaviour of basalt and gabbro in such systems, which dominate the Martian crust. This study uses a detailed petrologic investigation of an alteration event in a terrestrial analogue (Frankenstein Gabbro, Germany), combined with thermochemical modelling, to deduce a reaction path that is guided by ground truth, but independent of the terrestrial composition. Martian host rocks and fluids are substituted for the terrestrial model inputs, to predict the alteration of gabbro in an impact-induced system on Mars.

Alteration in the Frankenstein Gabbro mimics the fracture-controlled alteration expected in Martian impact craters, being focused along tectonically-induced, in situ of the fluids produced at high T, low W/R results in habitable fluids at T = 10–100 °C that are suitable for potential sulfide- and/or sulfate-utilising organisms.