Chemical Alteration and Soil Provenance of Polar Desert Sediments from the McMurdo Dry Valleys, Antarctica: An Analog for Alteration Processes on Mars

Abstract

The McMurdo Dry Valleys (MDV) of Antarctica are considered one of the best Earth-based environments for studying Mars on the basis of cold and dry surface conditions. It is through this analogy that investigations of potentially similar sub/surface processes have been established and researched. In an effort to determine type and degree of alteration processes across the past and present martian landscape, comprehensive elemental and mineralogical analyses were conducted on surface and core sediments across the MDV. Additionally, sediment provenance was investigated by analysis of Rare Earth Elements (REEs) and High Field Strength Elements (HFSEs) as a means to validate or refute alteration conclusions. Physical alteration, manifesting as wind erosion, mass-wasting, sediment-mixing, and freeze-thaw processes dominate at the surface of the MDV, but under unique conditions, including hypersalinity and/or ample surface cover, chemical alteration can dominate. Chemical alteration in the MDV was found to manifest as core sediment ranges with clays, sulfates, carbonates, or standing hypersaline surface waters. Investigations of sediment provenance primarily bolstered alteration conclusions, exhibiting relative depletions of HFSEs in samples that experienced heavy chemical alteration. Specific sites within the MDV are comparable to select Mars rover samples. Analysis of major elemental abundances, chemical alteration indices, and sulfite abundance show that the best analogy for the MDV to Mars is based on sulfate abundances, for which total sulfur and sulfite abundance can be a measure. Through this research we provide the means for further reconstruction of the martian paleoclimate and that of similar extraterrestrial environments.