^1,2Jitse Alsemgeest,¹Fraukje M. Brouwer,³Luis F. Auqué,¹Kirsten van Zuilen,⁴Natalia Hauser,⁴Wolf Uwe Reimold
Journal of Geophysical Research: Planets 131, e2025JE008966 Open Access Link to Article [https://doi.org/10.1029/2025JE008966]
¹Geology and Geochemistry Cluster, Department of Earth Sciences, VU Amsterdam, Amsterdam, The Netherlands
²Nowat GAIA, Faculty of Geo‐Information Science and Earth Observation, University of Twente, Enschede, The Netherlands
³Department of Geosciences, University of Zaragoza, Zaragoza, Spain
⁴Institute of Geosciences, University of Brasília,CEP, Brasília, Brazil
Published by arrangement with John Wiley & Sons

As hydrous minerals have been observed in impact craters on Mars, impact-generated hydrothermal systems (IGHSs) have been considered as potential habitats for life on that planet. The Vargeão Dome, a 12 km wide impact structure in southern Brazil, was formed in basalts with at least two hydrothermal alteration stages. This structure is a rare terrestrial analog for IGHS evolution on Mars. However, the thermochemical evolution of these stages and their relationship to the impact remain unresolved. Two vein-forming alteration stages were identified by multidisciplinary sample analysis of Vargeão Dome. Fractured and deformed white vein fragments from the first stage occur within red veins from the second. This suggests reactivation of the white vein set during the crater excavation and modification stages. Rare Earth Element and Rb-Sr isotope data indicate different fluid sources for the white and red veins and an evolving fluid system. Thermodynamic modeling indicates a cooling sequence from 100–250 to <25°C for the white vein set, whereas goethite and hematite within the red veins indicate that most IGHS activity occurred at temperatures below 40°C. Considering this and accounting for gravity differences, life-supporting IGHSs on Mars may preferentially form impact structures over 28 km in diameter. Furthermore, impact-reactivation suggests elevated habitat potential in structures with pre-existing fault, fracture, and vein systems. These occur in volcanic areas or terrain older than 3.5 Ga, when Mars was wetter and geologically active. Therefore, the search for evidence of IGHS-supported life should be focused on these kinds of terrains.