STRUCTURE OF HUSBAND HILL AND THE WEST SPUR OF THE COLUMBIA HILLS, GUSEV CRATER

The Mars Exploration Rover Spirit explored the West Spur and Husband Hill, the tallest of the Columbia Hills, for one Martian year before moving on to spend the majority of her mission at Home Plate. The formation mechanism of the Columbia Hills remains enigmatic: the currently favored hypotheses are that they are part of a central peak formation, or the intersection of multiple crater rims. As Spirit traversed across the West Spur and Husband Hill, she encountered several substantial (~0.5-10m) outcrops that are interpreted to be exposures of local bedrock. It is not known whether these units are part of the original Columbia Hills edifice, or were deposited after the Hills attained their current form. By characterizing the potentially planar surfaces, which may be bedding planes, displayed in these outcrops, we can test hypotheses regarding the emplacement of the current surface material, and the formation of the Columbia Hills.

We present the structure of the West Spur and Husband Hill as determined by measuring strikes and dips at numerous locations along the rover’s traverse. We additionally present Digital Terrain Models (DTMs) and planview maps of the outcrops and their surroundings, which we have made using stereo imaging data from the rover’s Navcam cameras. We measure the orientations of the Husband Hill and West Spur outcrops by examining hundreds of fine-scale (~1-100cm) features using DTMs derived from the rover’s Pancam and Navcam stereo imaging data. We include a rigorous error analysis, and compare the measured orientations to local and regional topography in order to test the hypothesis that the exposures Spirit observed on her traverse are representative of units that drape the Columbia Hills edifice.