Dissertation/Thesis Abstract

Geochemical Analysis of Soils from Extreme Environments on Earth and Mars
by Stroble, Shannon T., Ph.D., Tufts University, 2011, 349; 3487107
Abstract (Summary)

Geochemical analysis of soils, including the determination of pH, salinity and organic content can provide insight into the environmental history and habitability of the region from which they are collected. This dissertation focuses on the geochemical analysis of soils from three extreme environments: the North Polar Region of Mars, the McMurdo Dry Valleys (MDV) of Antarctica, and the Atacama Desert in Chile. Also included is a novel instrument for the electrochemical analysis of Martian soils for total organic carbon.

The Wet Chemistry Laboratory (WCL) aboard the 2007 Phoenix Mars Scout Lander performed the first aqueous analysis of the Martian soil. WCL found a slightly alkaline soil dominated by soluble sulfate, perchlorate, magnesium and sodium with contributions of soluble potassium, calcium and chloride. The discovery of perchlorate on Mars suggests the presence of oxidizing chemistry in either the atmosphere or soil.

The MDV and the Atacama are good terrestrial analogs for Mars, with all three environments possessing similarities in climate and topography. Soil samples from the Atacama Desert and MDV were analyzed to determine their chemical properties. Soils in both environments exhibit similar ionic species and pH. Most interestingly, perchlorate was found at the microgram per kilogram level in all soils from the MDV stable upland microclimate zone. This helps strengthen the argument that perchlorate is ubiquitous on Earth and accumulates only in hyperarid regions. The chemical properties of the soils from both of these extreme environments were compared to the properties of the Martian soil as determined by WCL. Neither environment's soil was drastically different from Mars. However, the soils from the stable upland climate zone in the MDV were found be the better terrestrial analog for the Martian soil at the Phoenix Lander site.

One vital piece of information about the soil composition on Mars has yet to be discovered, the amount of organic material present. The Mars Organic Carbon Analyzer (MOCA) is an alternative approach to determine Martian soil organic content. A prototype instrument has been developed and initial tests of its viability are described.

Indexing (document details)
Advisor: Kounaves, Samuel P.
Commitee: Kenny, Jonathan E., Marchant, David R., Utz, Arthur L.
School: Tufts University
Department: Chemistry
School Location: United States -- Massachusetts
Source: DAI-B 73/03, Dissertation Abstracts International
Subjects: Soil sciences, Analytical chemistry, Geochemistry
Keywords: Atacama Desert, Extreme environments, Mars, Martian soil, McMurdo Dry Valleys, Total organic carbon
Publication Number: 3487107
ISBN: 9781267058874
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