Sources and sinks of clay minerals on Mars

The recent identification of clay minerals on the Martian surface using visible-near infrared reflectance spectroscopy has had a profound effect on our view of aqueous alteration on Mars. Smectite, chlorite, kaolin group, and serpentine group minerals have been detected using the CRISM and OMEGA spectrometers, with Fe/Mg-smectite and chlorite varieties being the dominant types discovered throughout the ancient crust. Aqueous, eolian, and impact processes have transported and recycled some of these clays such that their current locations may not accurately reflect their formation environments. However, detrital clays could prove useful for constraining transport pathways and sediment provenance. Here we discuss the impact craters and channels that comprise the Uzboi-Ladon-Morava system, including Holden, Eberswalde, and Ladon craters, which represents a large-scale sediment sink for clay minerals derived from the surrounding Noachian crust. This system contains thick deposits of clay mineral-bearing strata that likely record a wide range of alluvial, fluvial, lacustrine, and eolian processes that provide direct insight into the Martian clay cycle. Broad concepts of sediment sources, sinks, and sediment transport paths can be outlined using orbital data, but future in situ exploration of the Martian sedimentary rock record will be necessary to distinguish fully between detrital and authigenic clay minerals, and thus to determine environmental conditions and transitions on ancient Mars.