A Study of the Sulfur Isotopic Composition of Martian Meteorites

dc.contributor.advisorFarquhar, Jamesen_US
dc.contributor.authorFranz, Heatheren_US
dc.contributor.departmentGeologyen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2012-10-10T11:27:42Z
dc.date.available2012-10-10T11:27:42Z
dc.date.issued2012en_US
dc.description.abstractABSTRACT Title of Document: A STUDY OF THE SULFUR ISOTOPIC COMPOSITION OF MARTIAN METEORITES Heather B. Franz, Ph.D., 2012 Directed By: Professor James Farquhar, Department of Geology and ESSIC Sulfur is an important tracer for geochemical processes because it possesses four stable isotopes and forms natural compounds in a range of oxidation states. This element has been shown to undergo mass-independent isotopic fractionation (S-MIF) during laboratory photochemical experiments, which may provide clues to processes that have occurred both in the solar nebula and in planetary atmospheres. The surface of Mars has been found to contain ubiquitous sulfate minerals, marking this planet as an ideal candidate for sulfur isotope study. The shergottites comprise the youngest group of martian meteorites and the most representative of mantle-derived igneous rocks. Extraction and isotopic measurement of sulfur from 30 shergottites yield the first estimate of the juvenile martian sulfur composition, which matches within uncertainties that of Cañon Diablo Troilite. Analysis of martian meteorites spanning a range of ages from the shergottites, as young as ~150 Ma, to the nakhlites, ~1.3 Ga, reveals the presence of sulfur characterized by S-MIF compositions. These findings are interpreted as evidence for cycling of sulfur between an atmospheric reservoir where photochemical processing of sulfur-bearing gases occurred and a surface reservoir in which photochemical products were ultimately deposited. Anomalous sulfur has been detected in both sulfate and sulfide minerals, implying assimilation of sulfur from the martian surface into magmas. Differences in the S-MIF compositions of the nakhlites and shergottites may preserve a record of complementary sulfur formed by a single process or may indicate the operation of multiple photochemical processes at different times or geographical locations. Identification of the photochemical mechanism responsible for producing the anomalous sulfur observed in martian meteorites is important for constraining the atmospheric composition at the time the S-MIF signals were generated. Results of laboratory experiments with pure SO2 gas suggest that self-shielding is insufficient to explain the anomalous sulfur isotopic composition. This implies that an optically thick SO2 column in the martian atmosphere may not have been required for production of the observed signalsen_US
dc.identifier.urihttp://hdl.handle.net/1903/13050
dc.subject.pqcontrolledGeochemistryen_US
dc.subject.pquncontrolledisotopeen_US
dc.subject.pquncontrolledMarsen_US
dc.subject.pquncontrolledmartianen_US
dc.subject.pquncontrolledmass-independenten_US
dc.subject.pquncontrolledmeteoriteen_US
dc.subject.pquncontrolledsulfuren_US
dc.titleA Study of the Sulfur Isotopic Composition of Martian Meteoritesen_US
dc.typeDissertationen_US

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