CRISM-Derived Spectral Scattering Parameters for Surfaces in the Vicinity of Opportunity Mars Rover Traverses

CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) data were used to retrieve scattering parameters of surfaces traversed by the Opportunity Mars rover, as well as adjacent areas. Our estimates agree with those retrieved by Johnson et al. [2006] using Opportunity's Panoramic Camera data, and we are able to extend estimates of the Hapke single particle scattering albedo and asymmetry parameter (from the one-term Henyey Greenstein single particle phase function) to a greater spectral resolution and spectral range. This analysis allows us to distinguish between surface units that otherwise look relatively uniform spectrally. This work also provides photometric functions essential for converting spectra to a single viewing geometry which will yield more accurate spectral comparisons. Our method involves simultaneously modeling surface and atmospheric contributions, iterating through surface scattering parameters until a Levenberg-Marquardt least squares best fit is achieved. Retrieved single scattering albedos range from 0.42 to 0.57 (0.5663 - 2.2715 micrometers), and retrieved asymmetry parameters range from -0.27 to -0.17 (moderately backscattering). All surfaces become more backscattering with increasing wavelength. Further, the northern and western portions of Victoria crater's ejecta apron are more backscattering than surrounding regions, indicating a change in physical properties. In images taken when the rover traversed this unit, a surface with small ripples and a dense cover of hematitic spherules is apparent, providing agreement with lab experiments by Johnson et al. [2006] showing increased backscattering with the addition of hematitic spherules. The CRISM-derived scattering parameters also show that bedrock-dominated surfaces are less backscattering than soil-covered surfaces.