Constraints on Paleohydrological Activities on Mars Derived from Delta Formation

Abstract Martian deltas record fluvial and sedimentary activity on early Mars. Yet, quantitative understanding of the hydrological and sedimentary processes underlying their formation remains limited. Here we quantitatively analyzed the fluvial and sedimentary processes of seven deltas exhibiting diverse morphologies across Mars. Our analysis is based on deltas and their channel features, from which we estimate paleo-discharge, sediment transport rates, depositional timescales, and the water volume required for delta formation. The deltas are classified into groundwater-sourced, precipitation-fed, and retreating-erosion types based on the geological context of their feeder channels and water sources. We propose that delta formation on Mars may have occurred under multiple scenarios, including retreating erosion, groundwater sapping, ice melting, precipitation-driven runoff, impact events, and variations in Martian obliquity. These scenarios suggest that prolonged warm climates were not a prerequisite for delta formation. Mass-balance calculations indicate that continuous delta formation timescales range from days to thousands of Martian years. However, accounting for likely intermittent water supplies and episodic flows, the overall formation timescales could extend to hundreds of millions of years. These findings provide a quantitative framework for interpreting paleo-sedimentary processes on Mars that may preserve important records of its geological and climatic history.