[1] On the basis of High Resolution Imaging Science Experiment (HiRISE) images of two successive years we observed changes of a gully on the Russell crater dune field. Within the first year the length of a ∼2 m wide incised gully channel grew about 50 m downslope, and ∼120 m within in the second year. Gully activity occurred in early spring between L S ∼198°and ∼218°in the first year and between L S ∼192°and ∼221°in the second year. Based on the channel morphology, spectral data and modeled surface temperatures, the changes can be best explained with transient melting of small amounts of H 2 O-ice triggering slurry flows consisting of sand mixed with liquid water. Citation: Reiss, D., G. Erkeling, K. E.Bauch, and H. Hiesinger (2010), Evidence for present day gully activity on the Russell crater dune field, Mars, Geophys. Res. Lett., 37, L06203,

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1] Several hundred occurrences of chloride-bearing salt deposits have been proposed in terrains within the southern highlands of Mars on the basis of Thermal Emission Imaging System and Thermal Emission Spectrometer infrared observations. The spectral identification of chloride salts by remote sensing is challenging because they are transparent over much of the thermal infrared portion of the spectrum. Further ambiguity arises from the diverse geologic settings in which the putative chloride-bearing materials are found. In order to better constrain the composition of these unique compositional units, we perform a global survey of these materials in the Near-Infrared (NIR) domain with the Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) imaging spectrometer. The spectral signatures of the deposits are consistent withalthough not specific ofchlorides. We do not observe olivine to be associated with the deposits, which confirms that sulfides are an unlikely alternative candidate. Our systematic search reveals the global lack of association with hydrated minerals (phyllosilicates, sulfates, hydrated silica) except for a few deposits (noteworthy in northwestern Terra Sirenum) where a small fraction of chloride material overlaps Fe/Mg-rich clay-bearing terrains. Even in these locations, the morphology and crosscutting relationships of the deposits suggest two separate episodes of mineralization, first phyllosilicates then chlorides, followed by subsequent formation of sulfates. Our study shows that local groundwater upwelling seems to be the most frequent source for the water involved in the formation of chloride, rather than surface runoff.