2007 GSA Denver Annual Meeting (28–31 October 2007)

Paper No. 3
Presentation Time: 8:45 AM


JOHNSON, Jeffrey R., Astrogeology Team, U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001, BELL III, James F., Cornell University, Ithaca, NY 14853 and FARRAND, William, Space Science Institute, boulder, CO 80301, jrjohnson@usgs.gov

The Mars Exploration Rovers (MER) Spirit and Opportunity carry four Panoramic Camera (Pancam) instruments (two per rover) that have obtained over 123,000 multispectral and stereoscopic images as of late June 2007, comprising over 107 Gbytes of data. These visible/near-infrared (443-1009 nm) color images have allowed the MER team to characterize the geology and mineralogy of materials along the rover traverses in Gusev crater and Meridiani Planum. Pancam images have been used for hazard identification and terrain modeling to guide rover navigation and tactical in situ sampling of targets by the instrument arm. Each Pancam consists of two digital cameras mounted on a mast 1.5 m above the martian surface. Pancam utilizes a 1024x1024 active imaging area frame transfer CCD detector array covering a 16x16 deg. field of view at 0.27 mrad/pixel scale. Pancam images are calibrated to: (1) absolute radiance (Wcm-2sr-1nm-1) using pre-flight data corrected for detector and electronics temperature variations; and (2) relative reflectance using observations of the Pancam Calibration Target and a model of the target's photometric behavior corrected for airfall-deposited dust. Near-simultaneous imaging of the target and scene also provides a first-order diffuse illumination correction for surfaces that are parallel to the target surface. Absolute uncertainties in relative reflectance are ~10%, whereas band-to-band uncertainties are 1-5%. Eighteen 360 deg. color panoramas and nearly 200 large color mosaics have been produced (http://marswatch.astro.cornell.edu/pancam_instrument/images.html). Recent Pancam investigations near the Home Plate pyroclastic structure in Gusev Crater include high albedo, white- to yellow-colored soils excavated by the rover wheels that exhibit spectral properties consistent with variably hydrated ferric sulfates and/or iron-poor, silica-rich materials. Opportunity's Pancam has investigated movement of basaltic sands emanating from the northern rim of Victoria Crater, along with detailed observations of aeolian cross-bedding in the sulfate-rich, sedimentary rock cliffs along the crater rim. Rock layers exhibit similar color properties in the walls of Victoria and Endurance craters, suggesting similar stratigraphic sequences and/or diagenetic history.