Phoenix Landing Site Hazard Assessment and Selection

The Phoenix Mars Scout landing site hazard assessment and selection process began with a survey of the latitude band from 65–72 N to identify candidate landing regions that were accessible, safe, and suitable for meeting the mission science objectives. Four candidate landing regions were identified based upon proximity of ground ice to the surface. Thermal inertia data, visible imagery, and topographicmapswere combined tomake an initial assessment of rock abundance and slopes. Broadly distributed high-resolution images enabled refined interpretation of the lowerresolution data sets. Based upon this assessment, a broad valley to thewest ofHeimdall crater at 68.3 N, 124.6 Wwas selected as the target landing region for the Phoenix mission. A detailed evaluation of this region resulted in the identification of eight different geologic units, with each unit exhibiting characteristic terrain type and rock abundances. Targeted high-resolution images were acquired across much of the region. An autonomous rockcounting algorithm was used to develop probabilistic risk distributions. Landing ellipse placement was selected to maximize the probability of a safe landing considering rock and slope hazards, including craters. Postlanding images from the Phoenix stereoscopic imager show a landing site generally devoid of hazardous rocks and slopes, consistent with predictions.