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Date of Award

Summer 8-15-2013

Author's School

Graduate School of Arts and Sciences

Author's Department

Earth & Planetary Sciences

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Orbital remote sensing data acquired from the Mars Express OMEGA and MRO CRISM instruments, in conjunction with other datasets, are used to perform detailed spectral and stratigraphic analyses with the goals of better understanding the mineralogy and aqueous history of deposits in Aram Chaos and south and southwest Melas Chasma on Mars. The Discrete Ordinate Radiative Transfer (DISORT) model is used to retrieve atmospherically and thermally corrected Lambert albedos from OMEGA I/F data for Aram Chaos and atmospherically corrected single scattering albedos from CRISM I/F data for Melas Chasma. Spectral analyses focus on detection, identification, and mapping of hydrated and/or hydroxylated alteration minerals in the visible-near to thermal infrared region (0.4-4.0 µm) for Aram Chaos and near infrared region (1.0-2.5 µm) for Melas Chasma.

In Aram Chaos, based on detailed reduction of OMEGA spectral data, focusing on use of DISORT-based radiative transfer procedures to model solar reflected and thermally-dominating spectral regions, together with stability and formation pathway considerations, we conclude that the spectral features in Aram Chaos are dominated by the presence of nanophase iron oxides, schwertmannite, and starkeyite. This mineral assemblage, together with gray, crystalline hematite previously detected from TES data [Glotch and Christensen, 2005], indicate that Aram Chaos has experienced iron oxidation and evaporation of iron-, magnesium-, and sulfur-rich fluids during periods of rising groundwater.

In the southern wall and nearby floor of Melas Chasma, a sequence of interbedded poly- and monohydrated sulfate layers associated with the interior layered deposits (ILDs) was identified using the data from CRISM and HiRISE imageries. The interbedded layers could have formed by a cyclic deposition of poly- and monohydrated sulfates during evaporation depending on brine salinity and variable water-to-rock ratios. A distinct jarosite-bearing unit was also identified in the topographically higher units near the hydrated sulfate deposits. The study area has apparently been through a period of acidic conditions resulting from an increase of volcanic volatile release or redox processes during episodes of groundwater upwelling, during which jarosite has formed by the evaporation of acid fluids that have altered basaltic materials, or through iron oxidation of subsurface fluids and subsequent precipitation.

To the southwest portion of Melas Chasma basin, hydrated sulfates and Fe/Mg smectites were both identified using CRISM hyperspectral data. Specifically the hydrated sulfate and Fe/Mg smectite deposits are interbedded and deposited at the bottom of the stratigraphic column, unconformably overlaid by a thick monohydrated sulfate unit. Geochemical modeling of coupled basalt weathering and fluid evaporation predicts that co-formation of smectites and sulfate evaporites in similar quantities, as observed in the interbedded smectite-sulfate sequence, is chemically plausible. The interbedded hydrated sulfate and Fe/Mg smetite deposits formed by the processes of repeated mechanical transportation of clastics by fluvial events, alteration by upwelling groundwater, and evaporation of the residual fluids.

Language

English (en)

Chair and Committee

Raymond Arvidson,

Committee Members

Jeffrey Catalano, Ramanath Cowsik, Jill Pasteris, Alian Wang, Brent Williams

Available for download on Tuesday, August 15, 2113

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