Origin and morphology of sinuous channels on the southwest rift apron of Ascraeus Mons and the surrounding plains, Tharsis, Mars

Ascraeus Mons is one of three large shield volcanoes in the Tharsis bulge region of Mars. The main flank of the volcano is bounded by rift aprons to the NE and SW. The SW rift apron is home to a network of complex sinuous channels whose origin has been debated in previous studies. Using high resolution spacecraft imagery, we use ArcGIS to map out all such channels on the NE quadrant of the rift apron as well as a number of similar features found on the plains to the east of Ascraeus Mons. We identify significant morphological differences between the sinuous channels on the proximal apron and the channels found on the distal apron but find that both types of channels are frequently associated with or transition into sinuous chains of collapse pits. The sinuous chains of collapse pits are interpreted as collapsed lava tubes on the basis of morphological similarities of such features in recent Hawaiian lava flows. Other Hawaiian lava flows exhibit features which are also found in the sinuous channels. This relationship between sinuous channels and lava tubes, which is consistent across the study area, suggests that the entirety of the sinuous channel features is volcanic in origin. The observed variation in morphology between the proximal and distal channels is proposed to be related to a difference in the gradient of the underlying surface, which is calculated using Mars Orbiter Laser Altimeter (MOLA) gridded elevation data.