부산대학교 도서관

Widespread valley networks (VNs) on Mars and other evidence point to an early warm and wet climate. However, ongoing debates still exist about VN's formation processes and associated climatic conditions. The power law relationship between basin length and area (Hack's Law) can be diagnostic of different fluvial processes related to climatic conditions. Past studies of Hack's Law on Mars at local sites have produced inconclusive results. Here we used a parameter‐free method to delineate watersheds globally on Mars based on mapped VNs and extracted their Hack's Law exponent (h). The majority of h values on Mars are similar to those in arid areas on Earth, suggesting similar runoff processes and arid conditions for VN formation on early Mars. Statistical analyses show that the spatial distribution of h on Mars is not random, but with a few clustered high and low values, likely controlled by local conditions (e.g., regional topographic slope). Plain Language Summary: Valley networks on Mars are river‐valley‐like features distributed primarily across the ancient cratered highland terrains. There are still debates on how they were formed and under what climatic conditions. We adapted an algorithm that only requires mapped valley networks and topography data as input to extract drainage basins on Mars and then examined the relationship between valley network length and drainage area (known as Hack's Law). We also replicated the same analysis to Earth for comparison. We found Hack's Law relationship for the majority of Martian watersheds to be similar to those of terrestrial watersheds formed in arid regions. The widespread distribution of Hack's Law relation on Mars similar to those of arid regions on Earth is consistent with Martian valley network formation by runoff erosion in an arid climate. Key Points: A parameter free Invasion Percolation Based Algorithm is adapted to delineate watersheds draining to mapped valley networks on MarsThe mean and standard deviation of Hack's Law exponent on Mars are similar to those of arid regions on Earth, suggesting similar climateSpatial statistics of Hack's Law exponent show clustered distribution, likely caused by regional topography and/or later modification [ABSTRACT FROM AUTHOR]