Testing the water hypothesis: Quantitative morphological analysis of terrestrial and martian mid-latitude gullies

•We compared terrestrial gullies with Martian mid-latitude gullies and dry ravines.•Our analysis indicated Martian and terrestrial gullies shared similar geomorphology.•The morphology of our studied Martian gullies is consistent with liquid water erosion.•Local geology and environmental conditions also heavily influenced morphology of all study sites.

Although Martian gullies resemble terrestrial counterparts, two conflicting hypotheses exist for their formation still invoke fluvial processes on the one hand or lubricated CO2 flows on the other. In this work we compared the quantitative morphology of terrestrial gullies, known to have formed by liquid water, and mid-latitude Martian gullies in the Martian southern hemisphere. We also compared these results with measurements of Martian dry ravines adjacent to the gullies. Our results show a similarity between Martian and terrestrial gully formation, supporting the hypothesis that liquid water was involved in their erosion. Our results show dry ravines differ morphologically from gullies, further suggesting fluidised flows as a likely origin of the latter. Variations in the relationships across various terrestrial and Martian gullies indicate the significance of local environmental and geological conditions. Our work supports the idea that Martian gullies may not have been formed by just one single process but may have evolved through a more complex interaction of processes and environment.