Mars Orbiter Camera observation of linear and curvilinear features in the Hellas basin: Indications for multiple processes of formation

The high resolution of the Mars Orbiter Camera images reveals many detailed landforms on Mars' surface, which include thin dark or bright linear/curvilinear features. The latter are generally only a few tens of meters wide but can be a couple of kilometers in length. Some of these features have previously been attributed to the action of dust devils. Our study of the linear/curvilinear features in the Hellas basin reveals a variety that can only be explained by the formation from many different processes. In order to evaluate different causes for their formation we created a mapping based on a classification scheme where the linear/curvilinear features were sorted into three groups and compared to terrestrial analogues. Features in group 1 are most frequent, and contain streaks that appear only to affect the ground surface. The best analogue is dust devil tracks. The second, very rare, group appears to penetrate the surface in a way expected of fractures. In the third, likewise rare, group the features have a topographic expression that makes them similar to grooves and/or trenches between narrow ridges. This group is probably formed by multiple processes. Possible terrestrial analogues are found in glacial and periglacial environments (e.g., glacial scouring, fluted moraine, cryoturbation patterns, and iceberg plow marks). The existence of such landforms in the Hellas basin is consistent with previously presented glacial models and has an important implication for the understanding of the past climatic evolution of Mars.