Manganese (Hydr)oxides record the dynamic evolution of a million-year Hesperian Ocean in Utopia Planitia, Mars

The duration and dynamic evolution of surface water on Mars are key to understanding its past habitability. Utopia Planitia, Mars' largest northern basin, preserves mineralogical signatures of ancient aqueous activity that remains chronologically unconstrained. Here, we present the quantitative reconstruction of the Hesperian Ocean's lifecycle using spectral analysis of manganese (Mn) (hydr)oxides as paleohydrological markers. Our innovative Spectral Contrastive-Aware Network, a deep learning framework trained on 13,742 infrared spectra of Martian soil simulants, decodes short-wave infrared data from China's Zhurong rover and orbiters operated by ESA and NASA. We identify altitude-dependent Mn (hydr)oxides enrichment that forms a distinctive mineralogical "bathtub ring", indicating an ancient ocean with defined boundaries. By quantitative mapping the spatiotemporal distribution of these minerals, we reconstruct the ocean's origin, expansion, regression, and extinction. Depositional modeling constrains its lifespan to 0.8-1.5 million years, providing the chronometrically constrained evidence for sustained surface water stability during the Hesperian.