Titan's upper atmospheric structure derived from Voyager ultraviolet spectrometer observations
AuthorVervack, Ronald Joe, 1966-
AdvisorSandel, Bill R.
MetadataShow full item record
PublisherThe University of Arizona.
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.
AbstractThe Voyager 1 Ultraviolet Spectrometer (UVS) observations are the only direct measurements we have of Titan's upper atmosphere. Previous analysis of the two UVS solar occultations yielded densities for N₂ CH₄ and C₂ as well as the thermospheric temperature. These results serve as the upper atmospheric boundary conditions in models of Titan's atmosphere; however, there are discrepancies between the observations and models, and the previous analysis itself is known to be internally inconsistent. We have undertaken a reanalysis of the UVS solar occultations to resolve these differences and to extract the maximum amount of information from the data. In so doing, we have developed a detailed model of the UVS detector and a new analysis method tailored to retrieving multiple species from an occultation of a finite-sized source such as the sun. Our analysis has yielded density profiles for nine species in Titan's upper atmosphere and a new measurement of the thermospheric temperature. We find higher N₂ densities and lower CH₄ and C₂ densities than those previously determined. We also find a thermospheric temperature of 150-155 K instead of 176-196 K as in the early analysis. Densities for C₂H₄, C₂H₆, C₄H₂, C₂N₂, HCN, and HC₃N are retrieved for the first time. Titan's atmosphere is one of the most interesting in the solar system. The composition and high degree of photochemical activity elicit comparisons to the early terrestrial atmosphere and considerations about the origins of life. Our results provide improved and expanded constraints for the atmospheric models and should provide scientists with a better view of Titan's upper atmosphere, which is important in planning for the upcoming Cassini mission.
Degree ProgramGraduate College