Geomorphology of the northern plains of Mars at the Phoenix mission candidate landing sites

In 2008, the Phoenix lander will touch down in the northern plains of Mars to sample and characterize near surface and underlying ice-rich soils, gather meteorological data, and provide insight into the evolution of the surrounding landscape. Three regions from 65 to 72°N and (A) 250-270°E, (B) 120-140°E, and (C) 65-85°E that meet mission engineering and scientific criteria were selected for detailed examination, with a targeted area within each region designated for additional high-resolution data acquisition. This dissertation focuses on the fine-scale geomorphologic characterization and mapping of these regions, and provides insight into surface modification processes at work at these high latitudes. Mars Orbiter Laser Altimeter (MOLA) topographic data, Thermal Emission Imaging System (THEMIS) visible and daytime infrared data, and Mars Orbiter Camera (MOC) data are utilized to produce geomorphologic maps at 36m/pixel for the larger regions and 18m/pixel for the targeted sites. Geomorphologic units provide context for MOLA and MOC-based slope calculations, and MOC data are examined for the occurrence of patterned ground. Region B THEMIS data are further analyzed to determine the crater cumulative size-frequency distribution in order to investigate possible resurfacing events.; Intercrater plains dominate all regions, with Polygonal Plains in Regions B and C composed of multiple kilometer-scale polygons while the Smooth/Mottled Plains in Region A commonly exhibits degraded thermokarst. Superposed on the plains units are Crater Interior and Crater Ejecta, with frequent rampart ejecta indicative of fluidized emplacement. The Knobby/Hill Terrain unit is defined on the basis of elevation; groups of small hills that occur in Region A are associated with the irregularly-shaped, shallow basins of the Depression unit, while hills in Regions B and C tend to be solitary. Finally, Crater Cluster Terrain is characterized by concentrated groups of small craters superposed on the plains in Regions B and C. In MOC data, decameter-scale patterned ground is observed on all geomorphologic units. Patterned ground, extremely low slopes, and widespread degradation are consistent with the long-term involvement of ground ice in surface modification processes. Crater size-frequency analysis results in Region B indicate that modification is limited to the upper few tens of meters.