The temporal changes in the emission spectrum of Comet 9P/Tempel 1 after Deep Impact

TL;DR

This study analyzes the time-dependent emission spectra of Comet 9P/Tempel 1 post-Deep Impact, revealing the formation and decay processes of various molecules, and provides insights into the comet's nucleus structure and composition.

Contribution

It introduces a detailed temporal analysis of emission spectra using modified Haser models, highlighting delayed gas emissions and their implications for cometary nucleus structure.

Findings

Prompt emission caused by initial impact and dust release.

Delayed gas emissions indicating secondary sublimation sources.

Insights into the comet's nucleus composition and structure.

Abstract

The time dependence of the changes in the emission spectra of Comet 9P/Tempel 1 after Deep Impact are 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(1S), OH, CN, C2, C3, NH, and NH2. 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(1S), CN, C2, C3, NH, and NH2 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 implications on the structure and composition of the comet's nucleus.