GEOLOGY OF MARS AS SEEN BY MRO/HIRISE

By July 2007 the High Resolution Imaging Science Experiment (HiRISE) acquired ~5 Tb of data in ~2,500 images of Mars at resolutions up to 25 cm/pixel in the 3 PM mapping orbit, covering ~0.1% of the surface. Early results include discovery or improved knowledge of (1) the stratigraphy of the polar layered deposits; (2) abundant boulders in unexpected places, including deposits previously interpreted as from airfall; (3) fractured mounds (possible ice-cored pingos) that have the same strong latitudinal distribution as gullies; (4) sublimation origin of scalloped surfaces near ±50º latitudes; (5) geology of past landing sites; (6) groundwater alteration along fractures in fine layered deposits [Okubo and McEwen 2006, Science 315, 983]; (7) fine-scale fractures and polygons in phyllosilicate-rich regions; (8) many small outcrops of light-toned layered rocks throughout the ancient highlands; (9) topographic data confirming the dust avalanche origin of slope streaks; (10) voluminous lava flowed through Athabasca Valles, then was deflated, and produced many lava-water interactions; (11) two major episodes of fluvial/lacustrine activity in Holden crater; (12) ancient megabreccia in Holden Crater, Nili Fossae, and other locations; (13) voluminous impact melts and debris flows from recent large (1-150 km) impact craters; (14) physical properties of bolides and Mars' atmosphere and surface from very recent (possibly MGS-era) impact craters; (15) relatively bright deposits associated with very recent activities associated with steep (~30º) gullied slopes; (16) fluvial processes in recent gullies and ravines; (17) current aeolian activity; (18) extensive glacial modification of the Argyre and Hellas regions; (19) seasonal changes and morphologies in the south polar region that constrain models for the evolution of these alien landscapes. We are planning continued production and analysis of meter-scale digital elevation models to test high-priority science questions.