Presently, Mars exists in a exceedingly hyper-arid state; however, geomorphic and now mineralogical and geochemical data obtained by Mars Exploration Rovers (MER) suggest the presence of a past and relatively wetter Mars. The MER results indicate that soils in modern, hyper-arid environments on Earth may serve as analogs to Mars soils. The presence of water under hyper-arid conditions can still facilitate, though limited, the geochemical cycling of a suite of elements that are easily solublized in aqueous solutions (e.g., S, Ca, Na, N, C). In order to develop models regarding the cycling and transport of these elements on Mars, terrestrial-based studies at the most arid-extremes are needed to develop quantitative insights, and interpretive models, for the growing Mars visual, chemical, and mineralogical data. In this project, we will examine the chemistry and mineralogy of soils in the Atacama Desert of northern Chile. The Atacama Desert of northern Chile is the driest desert in the world, with a hyper-arid climate that arguably has persisted since the Miocene. While Mars is vastly more dry and cold, the Atacama environment may be one of the best terrestrial Mars analogs easily accessible to researchers. Soils in the driest parts of the Atacama record the nearly abiotic, geochemical effects of long-term hyperaridity, where atmospherically-derived elements are retained in quantities rarely seen on Earth. The objectives of this work are to (1) assess both surface and subsurface distribution of elements and minerals [e.g., gypsum, anhydrite, nitratite (NaNO3) and calcite] in Atacama volcanic soils and (2) utilize results to inform the interpretation of present and on-going Martian soil data collection. Results from preliminary soil chemical and mineralogical data collected during the June, 2005 field trip to the Atacama will be presented.