Tabatha Heet
Washington University in St. Louis
Advisor: Raymond Arvidson

Abstract
A challenging aspect of Mars Exploration Program 2007 Phoenix landing site selection was locating an areally extensive region of low rock abundance. Odyssey THEMIS predawn thermal IR images to locate several areas of potentially low rock abundances were used. Based on the lack of warm surfaces we then used high resolution (~0.31m) Mars Reconnaissance Orbiter HiRISE images to map rock populations in some areas on a fine scale. Viking Lander 2 surface counts combined with Viking Lander 2 HiRISE counts were used to define the criterion for acceptable rock abundances as less than 18% cumulative fractional area covered by rocks. Initially rocks were counted by hand (hand-counts), but later a method of automatically characterizing rock distributions was developed (auto-counts). Hand-counts were used extensively to validate the auto-counting method. Auto-counts and hand-counts were used to support Monte Carlo landing simulations, which estimate the probability of successfully landing in an area with the given rock abundance. The chosen landing site had the highest probability of successfully landing based on Monte Carlo simulations and is located at 68.16 degrees north latitude, 233.25 degrees east longitude, within a ~50km wide by ~ 300 km long valley of relatively rock-free plains.