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Mineralogical and Geochemical Analyses of Antarctic Lake Sediments: A Reflectance and Moessbauer Spectroscopy Study with Applications for Remote Sensing on MarsLakebottom sediments from the Dry Valleys region of Antarctica have been analyzed here in order to study the influence of water chemistry on the mineralogy and geochemistry of these sediments, as well as to evaluate techniques for remote spectral identification of potential biomarker minerals on Mars. Lakes from the Dry Valleys region of Antarctica have been investigated as possible analogs for extinct lake environments on early Mars. Sediment cores were collected in the present study from perennially ice-covered Lake Hoare in the Taylor Valley. These sediments were taken from a core in an oxic region of the lake and another core in an anoxic zone. Differences between the two cores were observed in the sediment color, Fe(II)/Fe(III) ratio, the presence of pyrite, the abundance of Fe, S and some trace elements, and the C, N and S isotope fractionation patterns. The results of visible-infrared reflectance spectroscopy (0.3-25 microns) Mossbauer spectroscopy (77 and 4 K) and X-ray diffraction are combined to determine the mineralogy and composition of these samples. The sediments are dominated by plagioclase, K-feldspar, quartz and pyroxene. Algal mats grow on the bottom of the lake and organic material has been found throughout the cores. Calcite is abundant in some layers of the aerobic core (shallow region) and pyrite is abundant in some layers of the anaerobic core (deep region). Analysis of the spectroscopic features due to organics and carbonates with respect to the abundance of organic C and carbonate contents was performed in order to select optimal spectral bands for remote identification of these components in planetary regoliths. Carbonate bands near 4 and 6.8 microns (approx.2500 and 1500/cm) were detected for carbonate abundances as low as 0.1 wt.% CO2. Organic features at 3.38, 3.42 and 3.51 microns (2960, 2925 and 2850/cm) were detected for organic C abundances as low as 0.06 wt.% C. The d13C trends show a more complex organic history for the anaerobic sediments than for the aerobic sediments. The biogenic pyrite found in the anaerobic core is associated with lighter d34S values and high organic C levels and could be used as a biomarker mineral for paleolakes on Mars.
Document ID
20010084312
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Froeschl, Heinz
(Arsenal Research Vienna Austria)
Lougear, Andre
(Medical Univ. Luebeck Germany)
Trautwein, Alfred X.
(Medical Univ. Luebeck Germany)
Newton, Jason
(Tokyo Univ. Japan)
Doran, Peter T.
(Illinois Univ. IL United States)
Koerner, Wilfried
(Wien Univ. Austria)
Koeberl, Christian
(Wien Univ. Austria)
Bishop, Janice
DeVincenzi, Donald L.
Date Acquired
August 20, 2013
Publication Date
March 7, 2000
Subject Category
Geophysics
Funding Number(s)
PROJECT: RTOP 344-34-00-02
CONTRACT_GRANT: NCC2-1100
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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