Basal melting of snow on early Mars: A possible origin of some valley networks

Valley networks appear to be cut by liquid water, yet simulations suggest that early Mars could not have been warmed enough by a CO₂-H₂O greenhouse to permit rainfall. The vulnerability of an early atmosphere to impact erosion, the likely rapid scavenging of CO₂ from the atmosphere by weathering, and the lack of detection of weathering products all support a cold early Mars. We explore the hypothesis that valley networks could have formed as a result of basal melting of thick snow and ice deposits. Depending on the heat flow, an early snowpack a few hundred meters to a few kilometers thick could undergo basal melting, providing water to cut valley networks.