Impact-generated hydrothermal systems are considered a possible habitat for early life and are therefore of importance for the search of Martian life. To assess possible (past) impact-generated hydrothermal systems in Martian impact structures, two analogue structures on Earth, the Vargeão and Vista Alegre impact structures in Brazil, were compared to four Martian impact craters: Toro, Auki, Laylá, and Canso. Hydrothermal alteration, consisting of zeolites, celadonite and beidellite, in the Brazilian analogues was observed using hyperspectral data, in combination with optical and scanning electron microscopy data. Based on these data, a decision tree was developed to classify individual minerals. This decision tree was then applied to hyperspectral remote sensing data of the Martian craters. The classification of Toro crater shows clear signals of hydrous minerals: illite, celadonite, and beidellite(?). Other craters lack these signals. This lack of signals can be explained by shortcoming in (pre-)processed CRISM data and in the decision tree, differences in topographical resolution, dust cover, different origin of these hydrous minerals and differences in Martian and terrestrial hydrothermal systems. The developed decision tree is well applicable to terrestrial samples and CRISM data containing hydrothermal alteration, but must be combined with other methods to get a complete overview of hydrothermal alteration. Within the limitations of this study, a minimum crater size for an impact-generated hydrothermal system to occur on Mars is estimated around 30-40 km. Impact-generated hydrothermal systems most likely explain the occurrence of hydrous minerals in Martian craters, because the suggested impact-generated hydrous mineral, illite, is observed in Toro crater, while zeolites, which are likely excavated, are not observed in selected Martian craters.