| When exposed to stellar UV radiation, chemical processes will be governed not only by temperature/pressure but also the spectrum of the incoming dissociative photon flux; the system will approach kinetic, or photochemical, equilibrium, instead of thermochemical equilibrium. Over the previous decades, photochemistry has proven to be a powerful tool for predicting the chemical composition in the atmospheres of solar planets and their satellites. For example, the ozone layer in our own atmosphere (stratosphere) is a photochemical product of oxygen. In this thesis, I apply a photochemical model to the study of a variety of astronomical objects: the Earth, Jupiter, the Galilean satellite Callisto, and extrasolar "hot Jupiters" (HD 209458b). For the Earth, a method for utilizing the isotopic composition of CO2 and N2O to monitor global changes due to these two greenhouse gases is developed. For objects other than the Earth, the model facilitates in the interpretation of data acquired by remote (telescopic) and in situ (spacecraft) measurements. The ultimate goal is to understand the conditions of chemical and physical environments in protoplanetary nebulae, which will provide clues as to the formation of planetary systems; the synthesis of organic compounds which could lead to the appearance of life; and the evolution of planetary atmospheres such as the formation of Titan's nitrogen-rich atmosphere. |
