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dc.contributor.advisorLunine, Jonathan I.en_US
dc.contributor.authorNeish, Catherine Dorothy
dc.creatorNeish, Catherine Dorothyen_US
dc.date.accessioned2011-12-05T22:21:59Z
dc.date.available2011-12-05T22:21:59Z
dc.date.issued2008en_US
dc.identifier.urihttp://hdl.handle.net/10150/194180
dc.description.abstractSaturn’s moon Titan represents a unique locale for studying prebiotic chemistry. Reactions occurring in its thick nitrogen-methane atmosphere produce a wide variety of carbon, hydrogen, and nitrogen containing organic molecules. If these molecules are exposed to liquid water, they may react further to produce oxygen-containing species, a key step in the formation of terrestrial biomolecules. On average, Titan's surface is too cold for liquid water. However, models indicate that melting caused by impacts and/or cryovolcanism may lead to its episodic availability. One possible cryovolcanic dome, Ganesa Macula, was identified in early observations by the Cassini spacecraft. In this work, I estimate the height and morphology of this feature using a synthetic aperture radar (SAR) image. I then use a thermal conduction code to calculate the freezing timescale for an initially liquid dome, yielding freezing timescales of ~10² - 10⁵ years. To determine how far aqueous organic chemistry can proceed in liquid water environments on Titan, I measure the rate coefficients of Titan analogue organic molecules ("tholins") with low temperature aqueous solutions to produce oxygenated species. These reactions display first-order kinetics with half-lives between 0.4 and 7 days at 273 K (in water) and between 0.3 and 14 days at 253 K (in 13 wt. % ammonia-water). Tholin hydrolysis in aqueous solutions is thus very fast compared to the freezing timescales of impact melts and volcanic sites on Titan, which take hundreds to thousands of years to freeze. The fast incorporation of oxygen, along with new chemistry made available by the introduction of ammonia, may lead to the formation of molecules of prebiotic interest in these transient liquid water environments. This chemistry makes impact craters and cryovolcanoes important targets for future missions to Titan.
dc.language.isoENen_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.titleFormation of Prebiotic Molecules in Liquid Water Environments on the Surface of Titanen_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.contributor.chairLunine, Jonathan I.en_US
dc.identifier.oclc659750619en_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.contributor.committeememberLorenz, Ralph D.en_US
dc.contributor.committeememberSmith, Mark A.en_US
dc.contributor.committeememberPavlov, Alexanderen_US
dc.contributor.committeememberBrown, Robert H.en_US
dc.identifier.proquest10091en_US
thesis.degree.disciplinePlanetary Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.namePh.D.en_US
refterms.dateFOA2018-06-28T21:44:51Z
html.description.abstractSaturn’s moon Titan represents a unique locale for studying prebiotic chemistry. Reactions occurring in its thick nitrogen-methane atmosphere produce a wide variety of carbon, hydrogen, and nitrogen containing organic molecules. If these molecules are exposed to liquid water, they may react further to produce oxygen-containing species, a key step in the formation of terrestrial biomolecules. On average, Titan's surface is too cold for liquid water. However, models indicate that melting caused by impacts and/or cryovolcanism may lead to its episodic availability. One possible cryovolcanic dome, Ganesa Macula, was identified in early observations by the Cassini spacecraft. In this work, I estimate the height and morphology of this feature using a synthetic aperture radar (SAR) image. I then use a thermal conduction code to calculate the freezing timescale for an initially liquid dome, yielding freezing timescales of ~10² - 10⁵ years. To determine how far aqueous organic chemistry can proceed in liquid water environments on Titan, I measure the rate coefficients of Titan analogue organic molecules ("tholins") with low temperature aqueous solutions to produce oxygenated species. These reactions display first-order kinetics with half-lives between 0.4 and 7 days at 273 K (in water) and between 0.3 and 14 days at 253 K (in 13 wt. % ammonia-water). Tholin hydrolysis in aqueous solutions is thus very fast compared to the freezing timescales of impact melts and volcanic sites on Titan, which take hundreds to thousands of years to freeze. The fast incorporation of oxygen, along with new chemistry made available by the introduction of ammonia, may lead to the formation of molecules of prebiotic interest in these transient liquid water environments. This chemistry makes impact craters and cryovolcanoes important targets for future missions to Titan.


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