GEOMORPHIC MAPPING IN MARGARITIFER TERRA, MARS: MTM -15017

The Margaritifer Terra region of Mars (0 – 30°S/ 0 – 45°W) contains numerous features that suggest a complex fluvial history. Although the major fluvial feature in the region is the Uzboi-Holden-Ladon-Margaritifer (UHLM) outflow system that flows northward from Argyre basin to Ares Vallis, much of southeastern Margaritifer Terra has been influenced by the Samara-Himera and Paraná-Loire Valles systems. These systems are two of the most well-integrated valley systems on Mars and drain approximately 540,000 km2. The Samara-Himera and Paraná-Loire systems merge just south of Margaritifer basin where they join the UHLM system. In addition to fluvial features, Margaritifer Terra has been influenced by cratering, several resurfacing events, and volcanic activity that likely continued into the Amazonian.

Mapping in MTM -15017 is part of a larger project to map portions of Margaritifer Terra at the 1:500,000 scale. This mapping involves using MOLA topography, MOC wide angle and narrow angle images, THEMIS infrared and visible images, and HiRISE images to identify boundaries between different geomorphic units in order to unravel the history of events that have shaped the surface of this complex region.

MTM -15017 is directly northeast of Jones crater whose ejecta has affected the southwestern part of the quadrangle. The ejecta blanket and far-reaching rays of ejecta can be used to place various units in a relative dating sequence, and units overlain by ejecta include three different resurfacing events. Crater counting techniques have been used to confirm that these units are Hesperian in age, which correlates with previous large scale mapping of Margaritifer Terra. Another interesting feature in this area is a section of Loire Valles that flows from the southeast toward the northwest. Two parts of this section appear to be obscured by one of the resurfacing events. This places an important constraint on the timing of fluvial activity in the Loire system. Other interesting features include two areas of chaos which may be evidence for surface collapse resulting from the removal of subsurface ice. By mapping the boundaries of various geomorphic units in MTM -15017, we can gain a more complete understanding of the timing of resurfacing events, fluvial activity, and surface collapse in this part of southeastern Margaritifer Terra.