Dissertation/Thesis Abstract

Development and Characterization of Instrumentation for Future Extraterrestrial Soil Analyses: Investigation of Terrestrial Soil and Extraterrestrial Soil Analogues by Electrochemical Sensors and Ion Chromatography
by McElhoney, Kyle M., Ph.D., Tufts University, 2013, 161; 3599345
Abstract (Summary)

The research presented herein discusses the analysis of Martian soil from the Phoenix mission and the development of a new instrument to further our understanding of remote terrestrial and extraterrestrial environments. The focus of the Phoenix analysis work was placed on the quantification of the soluble sulfate in the Phoenix samples and the determination of perchlorate parent salts using modelling software, soil simulants, ion-selective electrodes and ion chromatography. The implications of these analyses, especially the presence of CaClO4, indicate an arid Martian environment at the Phoenix landing site.

Building on the successful Phoenix mission, as well as other un-flown instruments including the Robotic Chemical Analysis Laboratory, a new instrument was conceived, designed, and fabricated. The new instrument, the In-situ Chemical Analysis Laboratory and Sensor Array, increased the sampling capabilities compared with Phoenix by decreasing the size of the sample analysis unit while incorporating an increased number of sensors per unit. The scalable instrument can accommodate 4-100 units upon mass fabrication. Each sample analysis unit can house a maximum of 42 ion-selective electrodes, 3 reference electrodes, whilst reserving one wall for other electrochemical sensors. The increased sensor redundancy will allow for a more accurate and precise measurement of the soluble species present in the sample. The increased number of sensors was achieved by miniaturizing and optimizing the sensor design and materials. The final design, which utilized silver epoxy and porous carbon with an ion-selective membrane, yielded miniaturized sensors with similar sensitivity and stability while also increasing the overall lifetime.

An investigation into soil leaching parameters was also performed to investigate the effects of miniaturizing the sample analysis unit from accommodating 25 mL to less than 10 mL leaching solution. Ion chromatography showed that the greatest increase on the soluble species present in the leachate occurred as the leach ratio (g leach solution:g soil) and leach time increased for Antarctic soil samples. The low levels of calcium and magnesium resulted in the opposite trend, where the concentration was decreased as the leach ratio and time increased, due to the presence of carbonates in the leaching solution and soil sample.

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Indexing (document details)
Advisor: Kounaves, Samuel P.
Commitee: Bauer, Joseph, Sykes, Charles, Utz, Arthur L.
School: Tufts University
Department: Chemistry
School Location: United States -- Massachusetts
Source: DAI-B 75/02(E), Dissertation Abstracts International
Subjects: Paleontology, Soil sciences, Analytical chemistry, Geochemistry
Keywords: Electrochemistry, Instrumentation, Martian soil, Perchlorate parent salts, Phoenix mission, Sensors, Soluble sulfate
Publication Number: 3599345
ISBN: 978-1-303-48552-7
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