Quantitative analysis of the morphology of martian gullies and insights into their formation

The process of formation of observed geologically recent gully features on Mars has remained a topic of intense debate since their discovery. In this study, we performed quantitative morphological analysis on certain parameters of gullies from different settings, such as crater walls, terraces, and sand dunes, on the martian surface in addition to the Meteor and Xiuyan craters on the Earth. The morphometric parameters were measured for cross profiles, which were extracted along each gully at certain intervals. Some interesting relationships among the parameters were determined, which could provide us a comprehensive understanding of the morphologies of the gullies'. The results show that strong correlations exist among those parameters, and the gullies are morphometrically similar, except for a scale difference in different geologic settings. The morphometric similarity implies that they were probably formed by some common processes. On the other hand, the morphometric differences indicate that the processes may have played different roles in the formation of the gullies. The formation of gullies on the Earth crater walls was heavily affected by surface flow and slippage, and pre-existing fractures and faults were also very influential in their formation. We propose that gullies in martian crater walls and terraces should have a similar formation mechanism, and they can probably account for most of gullies appearing on crater walls. The morphometric differences between the gullies in sand dunes and other gully types are probably a result of the disparity in lithological settings, which have significant influence on erosion ability even for the same agents.