Origin of Sinuous Channels on the SW Rift Apron of Ascraeus Mons and the Surrounding Plains, Tharsis, Mars

By Zach Schierl
Whitman College, Walla Walla WA

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. Previous studies have looked in detail at single channels to determine the origin. Using spacecraft imagery and ArcGIS, we map out all such channels on the SW apron of Ascraeus Mons as well as a number of similar features found on the plains to the east of the volcano. We identify significant morphological differences between the sinuous channels on the proximal apron and the channels found on the distal apron. We discover that both types of channels are frequently associated with or transition into sinuous chains of collapse pits which are interpreted as collapsed lava tubes on the basis of previous studies of such features in recent Hawaiian lava flows. This relationship, which is consistent across the study area, suggests that the channels are volcanic in origin and that the observed variation in morphology is related to a difference in slope, which we calculate for each of the channels and tubes using Mars Orbiter Laser Altimeter (MOLA) gridded elevation data.