Date of Graduation

7-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Space & Planetary Sciences (PhD)

Degree Level

Graduate

Department

Space & Planetary Sciences

Advisor/Mentor

Chevrier, Vincent F.

Committee Member

Roe, Larry A.

Second Committee Member

Ulrich, Richard K.

Third Committee Member

Tullis, Jason A.

Keywords

Pure sciences; Earth sciences; Hydrocarbon; Saturn; Solar system; Spectroscopy; Titan

Abstract

Titan’s thick atmosphere is enriched with organic compounds and its surface holds reservoirs of hydrocarbons. This makes Titan the only other candidate in our solar system (apart from Earth) to have stable liquid at the surface. The stability and characteristics of liquid and ices on the surface of Titan are of high importance in understanding its surface-atmosphere interactions. Titan’s hydrological cycle is similar to what we see on Earth, with the exception of methane (CH4) and ethane (C2H6) taking the place of water. The smoggy atmosphere veils the surface of Titan from the view of Cassini spacecraft, except at seven atmospheric “windows” centered at 0.94, 1.07, 1.28, 1.59, 2.0, 2.7-2.8, and 5.0 μm. Using one of these atmospheric “windows” at 1.59 μm, the feature of acetylene (C2H2) has been identified in this study. Several studies in the past have speculated the presence of C2H2 with photochemical models and predicted it to exist on the surface of Titan forming hundreds of meter thick layer. The spectrum of C2H2 under simulated Titan conditions was collected in this study to unveil the surface of Titan as C2H2 rich. C2H2 and other solid compounds such as ethylene (C2H4) are thought to be abundant on Titan’s surface and soluble in liquid CH4 and C2H2, among the major compounds dissolved in the lakes. Using NIR spectroscopy techniques and numerical modeling, the solubility of C2H2 and C2H4 in methane and ethane has been estimated. C2H2 is highly soluble in ethane compared to methane whereas C2H4 is slightly more soluble in methane compared to ethane but almost an order of magnitude more soluble than C2H2. In the present work, the sublimation rate of methane ice and the freezing rates of methane and ethane have also been determined. Results suggest that after the rainstorm on Titan, liquid methane and ethane will freeze on the surface and then melt/sublimate. This process is in agreement with the recent observation from Cassini Spacecraft, as it observed the brightening and darkening of the surface after the rainstorm. The results of this dissertation proves the theory of

existence of acetylene on the surface of Titan as well as report constraints relating to the composition of lakes on Titan. The study also reports a spectral library of different hydrocarbons at Titan relevant conditions to analyze the recent and fourth coming Cassini spacecraft observations.

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