CRISM - FIRST RESULTS

During its first months of orbital operations, CRISM has acquired thousands of high-resolution observations of water-related deposits emplaced throughout Mars' history, and completed lower-resolution mapping of over half the planet. Preliminary results indicate greater compositional diversity than previously recognized, with dynamic environments persisting into recent Martian history. Noachian deposits exhibit more widespread and mineralogically diverse outcrops of phyllosilicate than had previously been recognized, in crater walls and eroded areas where buried materials have been exhumed. Different compositions are separated only by hundreds of meters, suggesting variations in alteration environments. In Hesperian layered deposits known previously to contain sulfates, CRISM resolves vertical compositional layering at the scale of individual layers, with different abundances and compositions of sulfate minerals. Such compositional stratification suggests temporal differences in depositional environments or post-depositional alteration processes. Amazonian deposits continue to show minimal evidence for liquid water. Recent gully deposits shown no evidence for hydrated minerals, although eroded slopes of the north polar layered deposits north polar layered deposits may show evidence for deposition of icy sediment by geologically young fluid flow. The polar layered deposits themselves exhibit complex vertical layering in the abundance and/or grain size of ice, and the underlying basal unit shows little evidence for ice and may be predominantly an eolian deposit. Monitoring of seasonal variations in the polar caps shows evidence for differential ablation and patchy redeposition of CO2 frost at scales as small as tens of meters.