The Temporal Changes In The Emission Spectrum Of Comet 9P/Tempel 1 After Deep Impact

Abstract

The time dependence of the changes in the emission spectra of Comet 9P/Tempel 1 after Deep Impact is derived and discussed. This was a unique event because for the first time it gave astronomers the opportunity to follow the time history of the formation and decay of O((1)S), OH, CN, C(2), C(3), NH, and NH(2). Least-squares fits of a modified Haser model with constraints using known rate constants were fit to the observed data. In the case of OH, a simple two-step Haser model provides a reasonable fit to the observations. Fitting the emissions from O((1)S), CN, C(2), C(3), NH, and NH(2) requires the addition of a delayed component to a regular two-or three-step Haser model. From this information, a picture of the Deep Impact encounter emerges where there is an initial formation of gas and dust, which is responsible for the prompt emission that occurs right after impact. A secondary source of gas starts later after impact when the initial dust has dissipated enough so that solar radiation can reach the surface of freshly exposed material. The implications of this and other results are discussed in terms of the structure and composition of the comet's nucleus.