The McMurdo Dry Valleys are the largest ice-free expanses of terrain on the Antarctic continent, roughly equal to the areal extent of Rhode Island.  While the surface geology of this unique geologic landscape has been studied since the early 1900s, small-scale heterogeneities in the mineralogy and geochemistry of the surface were difficult to characterize.  These local variations in surface composition best elucidate the geologic and environmental evolution of this region.  We utilized a suite of field techniques and laboratory analyses to fully characterize the chemical, mineralogical, and spectral variations observed throughout the McMurdo Dry Valleys.  Most unique is the use of orbital remote sensing techniques to map the spatial distribution of these properties across the region.  This resulted in the first spectral map of the McMurdo Dry Valleys, providing nearly 1.6 million multispectral data points that hold valuable information with regards to surface composition and thermophysical properties.

Spectral mapping using orbital datasets allows for identification of local compositional variations where traditional geologic mapping is difficult or impossible.  Additionally, multispectral visible, near-infrared, and thermal infrared data uncover compositional information that can only be observed with detailed laboratory analyses, which has been a significant limitation to traditional geologic field mapping. 

This study is the first use of orbital datasets for compositional investigation of the McMurdo Dry Valleys due to both difficulties in the removal of atmospheric contamination at high latitudes as well as the difficulties of ground validation in remote landscapes.  During two field campaigns in the McMurdo Dry Valleys, we collected hundreds of rock and regolith samples and analyzed their composition and spectral properties in laboratories across the United States.  These detailed laboratory investigations demonstrated the relationship between fundamental physical and chemical properties of rocks and sediments and their corresponding spectral signatures.

Standard model-based atmospheric correction techniques for visible and near-infrared datasets are inappropriate for use in remote polar locations due to scarcity of nearby atmospheric information, extreme local variations in weather and long solar path lengths through the atmosphere caused by low solar angles.  As a result, this study utilizes an in-scene atmospheric removal technique followed by validation using spectral measurements made in the laboratory and at select ground control points in the field.  The thermal infrared dataset was calibrated using its standard model-based technique, then validated using laboratory-derived spectral data, confirming the efficacy of this technique.

Utilizing this spectral dataset was pivotal in understanding the role of chemical alteration in hyper-arid and hypo-thermal terrestrial environments.  Unique spectral signatures observed in Beacon Valley, Antarctica, demonstrated the earliest documented stages of chemical alteration of regional volcanic rocks (Ferrar Dolerite).  The onset of chemical alteration is represented by the migration of positively charged cations to the rock surface and result in the oxidation of ferrous iron to ferric iron.  This transition is manifested by a discoloration of rock surfaces; unaltered rock interiors remain dark gray; their altered surfaces become red and brown.  The diffuse boundary between this alteration rind and the unaltered rock interiors demarcates the depth to which this atomic diffusion is no longer efficient.  On Earth, this process has only been observed in controlled laboratory environments where additional chemical alteration is not possible, or in unique geologic circumstances where alteration is halted by burial.&n...

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