Coordinated CRISM/Spirit Rover Measurements in the Columbia Hills, Gusev Crater, Mars

This paper summarizes coordinated observations using the CRISM hyperspectral imager (0.4 to 4 micrometers, 18 m/pixel) on the Mars Reconnaissance Orbiter and Spirit rover observations in the Columbia Hills of Gusev Crater. Spirit observations include discovery of outcrops (Voltaire) on Husband Hill that are interpreted to be aqueously altered impact melt deposits that incorporated local materials during emplacement. Evidence for extensive volcaniclastic activity and aqueous alteration in the Inner Basin includes cut and fill structures, cross bedding, fining upwards sequences, accretionary lapilli, and formation of sulfate, silica, and hematite-rich deposits. On the other hand, CRISM spectra for the Columbia Hills are controlled by the proportion of ferric-rich dust to ferrous-bearing igneous minerals exposed in ripples and other wind-blown deposits. The evidence for aqueous alteration derived from Spirit data is associated with outcrops too small to be characterized in detail from orbital observations or materials exposed from the shallow subsurface by the rover during its drives. Although orbital observations show many other locations on Mars with evidence for minerals formed or altered in an aqueous environment, Spirit data imply that the older crust of Mars has been altered even more extensively than evident from orbital data. This result greatly increases the potential that the surface or shallow subsurface was once a habitable regime.