Mapping Hydrated Materials with MER Pancam and MSL Mastcam: Results from Gusev Crater and Meridiani Planum, and Plans for Gale Crater

We have developed a "hydration signature" for mapping H2O- and/or OH-bearing materials at Mars landing sites using multispectral visible to near-infrared (Vis-NIR) observations from the Mars Exploration Rover (MER) Panoramic Camera (Pancam). Pancam's 13 narrowband geology filters cover 11 unique wavelengths in the visible and near infrared (434 to 1009 nm). The hydration signature is based on a strongly negative slope from 934 to 1009 nm that characterizes the spectra of hydrated silica-rich rocks and soils observed by MER Spirit; this feature is likely due to the 2ν1 + ν3 H2O combination band and/or the 3vOH overtone centered near ~1000 nm, whose positions vary slightly depending on bonding to nearest-neighbor atoms. Here we present the ways we have used this hydration signature, in combination with observations of morphology and texture, to remotely identify candidate hydrated materials in Pancam observations. At Gusev Crater, we find that the hydration signature is widespread along Spirit's traverse in the Columbia Hills, which adds to the growing body of evidence that aqueous alteration has played a significant role in the complex geologic history of this site. At Meridiani Planum, the hydration signature is associated with a specific stratigraphic layer ("Smith") exposed within the walls of Victoria Crater. We also discuss limitations to the use of the hydration signature, which can give false detections under specific viewing geometries. This hydration signature can similarly be used to map hydrated materials at the Mars Science Laboratory (MSL) landing site, Gale Crater. The MSL Mast Camera (Mastcam) is a two-instrument suite of fixed-focal length (FFL) cameras, one with a 15-degree field of view (FOV) and the other with a 5.1-degree FOV. Mastcam's narrowband filters cover 9 unique wavelengths in the visible and near-infrared (band centers near 440, 525, 675, 750, 800, 865, 905, 935, and 1035 nm), and are distributed between the two FFL cameras. Full-filter multispectral observations of the region of overlap between the two cameras can be used for our hydration signature mapping. Mastcam's longest-wavelength filter should be able to detect hydrated and/or hydroxylated minerals with strong absorptions between ~990 and ~1080 nm; because of the width of this IR filter, Mastcam will be sensitive to more H2O and/or OH-bearing species than Pancam. Here we summarize the minerals Mastcam should be able to detect if present at Gale Crater, and our plans for hydration signature mapping with MSL.