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dc.contributor.advisorBrown, Robert Hen_US
dc.contributor.authorPalmer, Eric Edward
dc.creatorPalmer, Eric Edwarden_US
dc.date.accessioned2011-12-05T22:25:37Z
dc.date.available2011-12-05T22:25:37Z
dc.date.issued2009en_US
dc.identifier.urihttp://hdl.handle.net/10150/194263
dc.description.abstractVolatiles are critical in understanding the history of the solar system. We conducted two case studies intended to further this understanding. First, we analyzed the presence of CO2 on Iapetus. Second, we evaluated aqueous alteration in CM chondrites.We studied the distribution, stability and production of CO2 on Saturn's moon Iapetus. We determined that CO2 is concentrated exclusively on Iapetus' dark material with an effective thickness of 31 nm. The total CO2 on Iapetus' surface is 2.3x108 kg. However, CO2 should not be present because it has a limited residence time on the surface of Iapetus. Our thermal calculations and modeling show that CO2 in the form of frost will not remain on Iapetus' surface beyond a few hundred years. Thus, it must be complexed with dark material. However, photodissociation will destroy the observed inventory in ~1/2 an Earth year.The lack of thermal and radiolytic stability requires an active source. We conducted experiments showing UV radiation generates CO2 under Iapetus-like conditions. We created a simulated regolith by mixing crushed water ice with isotopically labeled carbon. We then irradiated it with UV light at low temperature and pressure, producing 1.1x1015 parts m-2 s-1. Extrapolating to Iapetus, photolysis could generate 8.4x107 kg y-1, which makes photolytic production a good candidate for the source of the CO2 detected on Iapetus.We also studied the aqueous alteration of metal-bearing assemblages in CM chondrites. We examined Murchison, Cold Bokkeveld, Nogoya, and Murray using microscopy, electron microprobe analysis and scanning electron microscopy. Alteration on CM meteorites occurred within at least three microchemical environments: S-rich water, Si-rich water and water without substantial reactive components. Kamacite alters into tochilinite, cronstedtite, or magnetite. Sulfur associated alteration can form accessory minerals: P-rich sulfides, eskolaite and schreibersite.Additionally, we determined that there were two alteration events for some CM chondrites. The first formed a hydrated matrix prior to accretion, indicated by unaltered kamacite surrounded by a hydrated matrix. The second occurred after parent body formation. This event is indicated by large regions with consistent alteration features, surrounded by other regions of less altered material.
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.subjectCarbon Dioxideen_US
dc.subjectCarbonaceous Chondritesen_US
dc.subjectIapetusen_US
dc.subjectIceen_US
dc.subjectMeteoritesen_US
dc.subjectPhotochemistryen_US
dc.titleVolatiles on Solar System Objects: Carbon Dioxide on Iapetus and Aqueous Alteration in CM Chondritesen_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.contributor.chairBrown, Robert Hen_US
dc.identifier.oclc659753514en_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.contributor.committeememberLauretta, Dante Sen_US
dc.contributor.committeememberYelle, Rogeren_US
dc.contributor.committeememberLunine, Jonathan Ien_US
dc.contributor.committeememberBoynton, Williamen_US
dc.identifier.proquest10719en_US
thesis.degree.disciplinePlanetary Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.namePh.D.en_US
refterms.dateFOA2018-08-24T23:49:02Z
html.description.abstractVolatiles are critical in understanding the history of the solar system. We conducted two case studies intended to further this understanding. First, we analyzed the presence of CO2 on Iapetus. Second, we evaluated aqueous alteration in CM chondrites.We studied the distribution, stability and production of CO2 on Saturn's moon Iapetus. We determined that CO2 is concentrated exclusively on Iapetus' dark material with an effective thickness of 31 nm. The total CO2 on Iapetus' surface is 2.3x108 kg. However, CO2 should not be present because it has a limited residence time on the surface of Iapetus. Our thermal calculations and modeling show that CO2 in the form of frost will not remain on Iapetus' surface beyond a few hundred years. Thus, it must be complexed with dark material. However, photodissociation will destroy the observed inventory in ~1/2 an Earth year.The lack of thermal and radiolytic stability requires an active source. We conducted experiments showing UV radiation generates CO2 under Iapetus-like conditions. We created a simulated regolith by mixing crushed water ice with isotopically labeled carbon. We then irradiated it with UV light at low temperature and pressure, producing 1.1x1015 parts m-2 s-1. Extrapolating to Iapetus, photolysis could generate 8.4x107 kg y-1, which makes photolytic production a good candidate for the source of the CO2 detected on Iapetus.We also studied the aqueous alteration of metal-bearing assemblages in CM chondrites. We examined Murchison, Cold Bokkeveld, Nogoya, and Murray using microscopy, electron microprobe analysis and scanning electron microscopy. Alteration on CM meteorites occurred within at least three microchemical environments: S-rich water, Si-rich water and water without substantial reactive components. Kamacite alters into tochilinite, cronstedtite, or magnetite. Sulfur associated alteration can form accessory minerals: P-rich sulfides, eskolaite and schreibersite.Additionally, we determined that there were two alteration events for some CM chondrites. The first formed a hydrated matrix prior to accretion, indicated by unaltered kamacite surrounded by a hydrated matrix. The second occurred after parent body formation. This event is indicated by large regions with consistent alteration features, surrounded by other regions of less altered material.


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