Abstract EANA2026-237

While it is widely accepted that liquid water existed on Mars, the exact nature of its ancient environments remains a subject of intense debate. Traditional models suggest a broad climatic and geochemical transition from a relatively warm and wet Noachian, dominated by neutral-to-alkaline waters, to a progressively colder and drier Hesperian characterized by more localized and acidic aqueous systems (e.g., Bibring et al., 2006). However, recent in-situ robotic exploration has challenged this simplistic two-stage paradigm, revealing a more complex, multi-stage, and site-dependent Noachian-Hesperian transition. Constraining the environmental and geochemical evolution of early Mars is crucial, as it carries profound implications for the planet's past habitability and the potential emergence of life (e.g., Grotzinger et al., 2014). Yet, interpretations of Martian data are often fragmented, localized, or contrasting. To contribute to a more integrated interpretation of the processes which shaped the Martian surface, we investigated two terrestrial aquatic systems characterized by contrasting pH, distinct geochemical water-rock interactions, and diverse biological activity. The two selected field sites are: 1) Bagno dell’Acqua lake (BA), located on the island of Pantelleria (southern Italy), and 2) Solforata di Pomezia (SP), near Rome (central Italy). BA is characterized by alkaline waters with pH = ~9 throughout the lake, decreasing to ~6 in the associated thermal pools and active co-precipitation of carbonates and phyllosilicates. Conversely, SP features extremely acidic waters (1 < pH < 4) with a mineralogy rather dominated by sulfates, Al-phyllosilicates and minor sulfides. The mineralogical associations observed in these two sites provide relevant terrestrial analogs for the aqueous environments inferred for Mars during the Noachian and the Hesperian respectively. Furthermore, both systems host complex and diversified biological communities, providing an ideal opportunity to explore the interplay between geochemistry, mineralogy, and biological activity. To this end, we sampled and analyzed representative rocks and soils to define their mineralogical composition and characterize the resident microbial communities. Our results help constrain the spectral and geochemical dataset from Mars and refine our understanding of the environmental transition from neutral to alkaline to acidic aqueous systems, as well as the planet's potential for habitability. This work is timely given the ExoMars Rosalind Franklin mission, whose forthcoming surface and subsurface investigation will benefit from the integrated spectral, mineralogical and microbial constraints provided by these analogs.