Other
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p13b1380j&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P13B-1380
Other
[5464] Planetary Sciences: Solid Surface Planets / Remote Sensing
Scientific paper
The hyperarid (< 2 mm/yr MAP) Atacama Desert of northern Chile is a widely accepted terrestrial analog for the surface of Mars. Sulfate and chloride deposits are present in uncommonly high abundances throughout the Atacama. The formation and preservation of these evaporite deposits are a direct result of the arid-hyperarid climate of the region from the Triassic to the present. Mars, too, is known for a long history of aridity. Remotely sensed data from THEMIS, TES, and analyses conducted during Mars landing missions have revealed the presence of sulfate and chloride deposits covering some portions of Mars’ surface. We synthesize remotely sensed (ASTER) data from the Atacama with field observations and sample analyses by laboratory thermal spectroscopy and portable XRF to inform how best to interpret signatures of sulfate and chloride deposits on Mars. We focus on two salars, one ancient (Salar de Llamara) and one modern (Salar de Atacama), to better understand how evaporites’ spectral and geochemical signatures may evolve through time. The oldest deposits of the Salar de Llamara are Miocene in age, while the Salar de Atacama continues to develop today. Compositionally, both salars’ surfaces are dominated by sulfate (gypsum and anhydrite) and chloride (halite) deposits. We selected sample sites according to compositional boundaries inferred from decorrelation stretches of thermal infrared (TIR) ASTER bands supplemented by previous field reconnaissance. We collected surface samples along transects from the core of the salars to their shorelines, intersecting zones ranging from predominantly sulfate or chloride to near equal mixtures of each composition. This transect approach to sampling allowed us to collect samples that incorporated a range of both geochemical compositions and processes fundamental to the spatial and temporal evolution of evaporite deposits. Preliminary results show promise in refining our ability to identify sulfates and chlorides using lab spectra, and they agree with the results of other terrestrial analog efforts that focused on evaporite deposits. We also present our high spectral resolution results degraded to the coarse resolution (90 m/pixel) of ASTER’s TIR bands in order to understand the spectral signature of salar surfaces composed of some mixture of both sulfate and chloride. An improved understanding of how mixed spectral signatures of evaporites are expressed at the resolution of the TIR bands of ASTER and THEMIS is invaluable to further identification and interpretation of these deposits on Mars.
Amundson Ron
Christensen Per Rex
Edwards Christopher S.
Heimsath Arjun M.
Jungers M. C.
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