Constraints on paleo hydrological activities on Mars derived from delta formation

Deltas record fluvial and sedimentary activities on the early Mars. Yet, quantitative hydrologic and sedimentary processes related with their formation need further investigation. Here we quantitatively analysed the fluvial and sedimentary process of seven deltas exhibiting diverse morphologies across different Martian locations. Identification of Martian rivers from valleys formed the basis of our analysis, with estimates made for paleo discharge, sediment transport rates, timescales and requisite water for deltas construction. We considered various water supply processes, and classified the seven deltas into three types based on geological contexts of their supplying valleys and water source. We suppose that the delta formation potentially associated with various scenarios, including retreating erosion, groundwater sapping, ice melting, precipitation, impact events and variations in Martian obliquity, unveiling that a warm climate is not a fundamental requirement for the formation. Based on mass balances, the continuous formation timescales of these deltas range from days to thousands of Martian years. Considering the intermittency of water supply and flow dynamics, these timescales can extend to hundreds of millions of years. These findings allow for quantitatively analysing paleo-sedimentary processes that may preserve geological and climatic cues.