Thesis (Ph. D.)--University of California, Berkeley, Mayu 1921. / Bibliography: 2 leaves between p. 20 and 21.

Univ., Phil. Diss.--Jena, 1681. / "Ad. d. Martii Anno M.DC.XIXC."

Thesis (Ph. D.)--University of Toledo, 2005. / Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Physics." Includes bibliographical references (leaves 295-304).

Understanding the chemical composition of comets is of great interest to the scientific community. In this work, an integral field unit (IFU) spectrograph is used to detect emissions of C2, C3, CH, CN, and NH2. The azimuthal average profile (line integral of the column density as a function of radial distance from the center of the nucleus) is simulated by the Haser model. The Haser model simulates the outgassing and photo-dissociate of molecular species in the coma. In this work, the lifetime of the parent molecule in the photo-dissociation chain is set as a free parameter. The best fit parent lifetimes for observations of comets 4P/Faye, 10P/Tempel 2, and C/2009 P1 Garradd are obtained. The results are compared to parent lifetimes cited in other studies. HCN as a likely dominant parent for CN is eliminated. Constraints on likely parent molecules for C3 and NH2 are discussed.

This work is a part of a more global effort aimed at understanding and interpreting in situ and remote sensing data acquired by instruments on board Rosetta. This study aims at deriving the dust mass source rate and the location of the dust jet source observed by Rosetta VIRTIS-M on 2015 April 12. The analysis is performed by means of the coupled kinetic modelling of gas and dust in the coma of comet 67P/Churyumov-Gerasimenko, which were used for calculating the coma brightness as it would be seen from the Rosetta spacecraft. The dust mass production rate and a possible location of the jet origin needed to explain the Rosetta VIRTIS-M dust brightness image were inferred by comparing the calculated brightness with VIRTIS-M data. Our analysis suggests that the dust mass production rate needed to maintain the observed jet is about 1.9 kg s(-1). According to our analysis, the location of the observed jet surface footprint is outside of the nucleus area characterized by the highest gas production rate, which suggests that gas and dust source rates are not necessarily proportional to each other across the entire nucleus surface. The inferred location of the possible jet origin is consistent with that of the observed active pits. In this paper, we show that the jet intensity is variable in time, and has a lifetime of at least 10 h.

Thesis (Ph.D.)--Columbia University, 1916. / Description based on print version record. Vita. Bibliography: p. 120-126.

Cometary nuclei may be our best available probes of the physical and chemical nature of the presolar nebula. However, in situ sampling of cometary nuclei to determine their composition is generally not feasible. Instead, remote spectroscopic observations of cometary comae are used to infer cometary composition. This approach relies on one's ability to model accurately the density distributions of gas and dust in the comae and a complex network of photochemical and molecular processes. Previously, a variety of theoretical models had been developed and, unfortunately, they are applicable only to a portion of the coma or to specific problems. In the first part of this thesis we introduce a preliminary version of a gas model built upon the concepts of dilute gas theory. This model is valid over the whole coma and it incorporates all previous models as its special cases, thus providing a new theoretical foundation for future cometary studies. In the second part of the thesis we discuss a spectral outflow model. This model is a special case of the dilute gas model and is tailored specifically to retrieve kinematic properties of cometary comae from velocity-resolved spectral line profiles. We review the formation of cometary spectral line profiles and we develop an analytic expression that maps three dimensional number density distributions into synthetic spectral line profiles. After discussing simplifications and Monte Carlo computational procedures, we apply the spectral outflow model to interpret infrared observations of H₂O in comets Halley and Wilson.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographic references (leaves [106]-109).

Infrared observations of the coma of 67P/Churyumov-Gerasimenko were carried out from 2015 July to September, i.e. around perihelion (2015 August 13), with the high-resolution channel of the Visible and Infrared Thermal Imaging Spectrometer instrument onboard Rosetta. We present the analysis of fluorescence emission lines of H2O, CO2, (CO2)-C-13, OCS, and CH4 detected in limb sounding with the field of view at 2.7-5 km from the comet centre. Measurements are sampling outgassing from the illuminated Southern hemisphere, as revealed by H2O and CO2 raster maps, which show anisotropic distributions, aligned along the projected rotation axis. An abrupt increase of water production is observed 6 d after perihelion. In the meantime, CO2, CH4, and OCS abundances relative to water increased by a factor of 2 to reach mean values of 32, 0.47, and 0.18 per cent, respectively, averaging post-perihelion data. We interpret these changes as resulting from the erosion of volatile-poor surface layers. Sustained dust ablation due to the sublimation of water ice maintained volatile-rich layers near the surface until at least the end of the considered period, as expected for low thermal inertia surface layers. The large abundance measured for CO2 should be representative of the 67P nucleus original composition, and indicates that 67P is a CO2-rich comet. Comparison with abundance ratios measured in the Northern hemisphere shows that seasons play an important role in comet outgassing. The low CO2/H2O values measured above the illuminated Northern hemisphere are not original, but the result of the devolatilization of the uppermost layers.

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