Classification of Mars Pathfinder Rock Surfaces Using Quantitative Morphologic Indices

Background: The Mars Pathfinder (MPF) landing site was originally predicted to contain a broad sampling of rock types varying in mineralogical, physical, mechanical and geochemical characteristics. Although rocks have been divided into several spectral categories based on Imager for Mars Pathfinder (IMP) visi-ble/near-infrared spectra, it has not been fully determined which of these categories stem from intrinsic mineralogical differences between rocks or rock surfaces , and which result from factors such as physical or chemical weathering. This has made isolation of unique rock or rock surface mineralogies difficult. Efforts in isolating and classifying spectral units among MPF rocks and soils have focused on refining our understanding of the spectra returned by the IMP, including the removal of smaller and smaller instrument calibration errors with respect to the radiometric calibration target (e.g.[1, 2]), modeling the spectral contribution of atmospheric dust [3-6], improving our understanding of the interactions between the various illumination factors (e.g.[7]), producing digital terrain models of the topographic variations on the surface and on rocks to correct for differences in spectral signature due to illumination angle (e.g.[8]), and attempting to spectrally isolate the effects of mantling dust [5, 6, 9]. These efforts have met with varying degrees of success, and the current state of understanding of each possible factor influencing spectral signature is such that many cannot currently be quantified to a sufficient level so they may be removed. The result of this fact is that many fundamental questions regarding information needed to reveal the present and past interactions between the rocks and rock surfaces and the Martian environment remain unanswered. Approach and Method: It is possible to approach the issue of identifying the existence and distribution of distinct rock and rock surface types from a different angle. Morphology is another characteristic that is dependent upon the intrinsic properties and geologic and weathering history of rocks, among other things, and can be assessed quantitatively as a tool to diagnose various rock types in a scene. Correlated with spectral data, the use of both characteristics provides constraints on the number of rock and rock surface types at the MPF landing site. We have examined the morphology of rocks in two regions of the MPF landing site in terms of location, size and dimensions, spheric