Flow deposits laid down on Mars within the last few years look like they were laid down by flowing water. In this paper, Pelletier et al. test this hypothesis by computer modeling of water-based versus dry landsliding. Dry landslides can "fluidize" under certain conditions and appear as though they were laid down by water. Model results show that the observed deposit on Mars was most consistent with a dry landsliding process. This has important implications in the debate about the presence/absence of liquid water on the surface of Mars today.
Nanometer-scale complexity, growth, and diagenesis in desert varnish
Laurence Garvie et al., Center for Meteorite Studies, School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287, USA. Pages 215-218.
Finely layered coatings, rich in manganese and iron and commonly called desert varnish, are common on rocks in desert environments worldwide. These coatings have been the subject of intense scientific debate and extensive research, owing to their potential for indicating past climates, for dating geological surfaces, and, via artwork carved in varnish, for providing information about ancient cultures. The full scientific potential of desert varnish can only be realized through a rigorous probing of the physico-chemical variables and fundamental properties of varnish components, especially its mineralogical components. Determining the mineralogy of the manganese- and iron-bearing materials is challenging because the minerals are extremely fine grained, generally down to nanometer-sized, and often poorly crystalline. In addition, the thin film-like nature of varnish on rock makes separating and studying it difficult. Garvie et al. used novel sample preparation methods, high-resolution electron microscopy, and spectroscopic imaging to provide novel insights into desert varnish structure, mineralogy, and chemistry. The spectroscopic imaging sho
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Geological Society of America