Constraints on the Noachian Paleoclimate of the Martian Highlands From Landscape Evolution Modeling

Abstract The progressive degradation and loss of impact craters throughout the Noachian Period on Mars indicate prolonged erosion, rather than only a brief spike around the Noachian/Hesperian transition. The purpose of this study is to determine which suite(s) of geomorphic processes and rates best reproduce the relict Noachian landscape. We modeled the evolution of two study areas in the Martian highlands, Noachis Terra and Terra Cimmeria, to constrain the long‐term erosional processes and rates that prevailed ~4.0–3.7 Ga, before the valley networks formed. Our model runs indicate a very low erosion rate and inefficient runoff production during the Middle and Late Noachian Epochs. The terrestrial equivalent of 2 and 1.5 Myr worth of erosional work under arid to semiarid conditions with inefficient runoff production was required in order to replicate the landscape at Noachis Terra and Terra Cimmeria, respectively, over ~300 Myr. Low areas in the landscape filled with sediments, while mass wasting and fluvial erosion were focused on crater rims and interior walls. The surface characteristics that best reproduce the observed landscape are a bedrock weathering rate around 0.0005–0.001 m/year with regolith that is 100 times more erodible than bedrock, suggesting that impact comminution and aqueous weathering produced abundant transportable material on Noachian Mars. The simulation results suggest that the Noachian paleoclimate was more arid than around the Noachian/Hesperian transition, but it supported occasional precipitation (snow or rain) that weathered surface materials and transported sediments.