The volume of water required to carve the martian valley networks: Improved constraints using updated methods

The martian valley networks are a key piece of evidence for the presence of liquid water on early Mars, and understanding their formation conditions can provide valuable insight into the nature of the early climate. Previous studies have used various methods to estimate the volume of water required to carve the valley networks, with results ranging from 3-5000 m Global Equivalent Layer (GEL). In comparison, other workers have found that the surface/near-surface water inventory was likely to have been ∼24 m GEL at the Noachian-Hesperian boundary. Thus, 3 m GEL may be consistent with recycling in a cold and icy Late Noachian-Early Hesperian climate, while 5000 m GEL may require continuous warm and wet conditions. In this study, we use updated methods and datasets to better constrain the necessary volume of water, finding a conservative lower limit of 640 m GEL. Based on valley network formation timescales, we find that our results do not preclude a cold and icy Late Noachian-Early Hesperian climate. Thus, this updated estimate of the minimum volume of water required to carve the valley networks is consistent with both formation in a cold and icy and warm and wet climate.