RECENT ADVANCES IN MARS TECTONICS THROUGH THE EYE OF HIRISE

HiRISE data are revealing a new scale of opportunities for studying the tectonic evolution of Mars. Since the beginning of MRO's Primary Science Phase in November 2006, HiRISE has imaged the surface of Mars at pixel widths of 24 to 36 cm, and with signal to noise ratios that are typically better than 100:1. At this scale and fidelity, fractures with sub–meter displacements can be detected and meter–scale displacements can be resolved.

Analyses of these data have revealed the along–strike displacement distributions for joints in layered deposits and dikes in the wall rock in Valles Marineris. These profiles show how opening–mode displacements scale with fracture length on Mars and have enabled calculations of material strength from fracture population strain. Digital elevation models from stereo HiRISE observations will enable more extensive measurements of bedding attitudes, fault orientations and sense of offset, and fault displacement distributions.

A notable recent finding is the identification of deformation bands in equatorial layered deposits. This class of discontinuities is an important precursor to the development of frictionally slipping faults in granular materials. Additionally, the damage zones and process zones that these bands form are known to act as either impediments or conduits to fluid flow in subsurface reservoirs on Earth. Thus recognition of deformation bands on Mars is a significant step toward unraveling the history of faulting and groundwater migration through the planet's layered sedimentary deposits.

HiRISE color data allows for spatial variability in albedo due to compositional variation to be discerned from topographic shading. Based on this color data, evidence of bleaching and cementation along fractures within the layered deposits of Candor Chasma was recognized in one of the earliest HiRISE images. Subsequent imagery has revealed that evidence of bleaching, staining by dark toned precipitates, and preferential induration along faults and fractures is common throughout the layered deposits of not only Valles Marineris, but also elsewhere such as in Meridiani Planum and Nili Fossae. Insight into the evolution of groundwater chemistry over time, and implications for past habitability and future landing site selection, will be gained through analyses of these diagenetic fingerprints.