Origin of Late Noachian‐Early Hesperian Valley Networks on Mars: Insights From Landform Evolution and Ice Sheet Modeling

Abstract Dendritic valley networks on Mars have been cited as evidence for a warm and wet Noachian Mars, permitting rainfall precipitation and surface runoff. However, the climatic conditions required to sustain rainfall on early Mars remain debated. In particular, climate models that produce significant rainfall commonly require a denser CO 2 atmosphere, additional greenhouse warming from reducing gases, and substantial surface water reservoirs. In contrast, some model configurations predict very low global mean annual temperatures, snow accumulation, and ice sheet development in the equatorial southern highlands. In this study, we simulate both endmember scenarios for three well‐preserved, highly dendritic valley networks: Warrego Valles, Terra Cimmeria, and Parana Valles. For the ice‐sheet case, we model meltwater from a fixed terminus, representing an oversimplified ice‐sheet scenario for use as a diagnostic benchmark, and a time‐varying terminus, which is consistent with results from ice‐sheet modeling. For the rainfall precipitation‐runoff scenario, we tested uniform and elevation‐dependent precipitation. We then delineate the model‐produced valley networks and quantitatively analyze the results. Our results show that the advancing and receding ice sheet scenarios driven by obliquity cycles can generate the same morphometric signatures as rainfall. These findings address a key geomorphology‐based objection to the ice‐sheet hypothesis, showing that dynamic ice‐sheet melt cannot be excluded based on valley morphology alone. While rainfall remains consistent with the observed valley network forms, our results demonstrate that ice‐sheet melt is also geomorphologically viable under obliquity‐modulated melting regimes.