Morphological and morphometrical differentiation of processes on crater walls in Eastern Utopia Planitia, Mars

Abstract

This study identifies a variety of processes associated with erosional and depositional structures within impact craters in eastern Utopia Planitia, Mars. Differentiation of the morphological characteristics of erosional and depositional structures within five structures suggests that four types of landforms develop on craters walls: debris flows, linear or dendritic channels resembling gullies, head-cut channels, and dry flows. Previous studies have mostly focused on the orientation characteristics of gully-type landforms and the environmental conditions that contributed to their formation. Most of these studies favored the term gully for all “wet” processes affecting crater walls, although debris flows have also recently been described. The full development of these structures shows that the wet-member structures (e.g., temporary channels resembling gullies) and mixed types (e.g., debris flows) evolved under different environmental conditions than that of present-day Mars. Dry flows can form in the current environmental conditions, but their presence near to the wet-member forms and the structural relationships among these wet and dry forms suggest that they formed within the same periods during fluctuations in atmospheric conditions. The morphometrical characteristics of flows on craters walls show that there is a relationship between the accumulation area and slope of processes, which indicate a morphometric threshold between the wet and dry types of erosion; with gully channels developing on low angle colluvial slopes while the debris flows are forming on more abrupt slopes. It is suggested that the most important controlling factors for flow initiation and development on the crater walls are first related to the morphometry of craters walls, and then to water availability and exposure of bedrock within crater walls.