Keck 1 HIRES observations of tempel 1 at the time of impact

Abstract

The Keck 1 HIRES observations of the Deep Impact event on July 4 have been qualitatively re-examined in an effort to isolate the changes in the HIRES spectra that can be attributed to the event itself. To accomplish this goal, background spectra due to ambient emission that was already present in the comet were extracted from the pixels at the end of the slit. This material can not have any emission from material that was produced at the time of the impact until at least several thousand seconds after the impact because it takes this long for the material to reach this distance from the nucleus. With the data extracted in this manner it can be shown that the spectra from OH, O (1S), CN, NH, NH2, C2, and C3 changed as a function of time after impact. In the spectra of all of these species there is evidence for a prompt change in the emission intensity that probably is due to the hot plume formed initially during the impact. After the first 600 s the time dependence of the intensities of the emission spectra species appear to be consistent with the photochemical formation and destruction of parents and daughters. The spectral changes with time associated with the CH emission appear to be unique in that the only change that is observed is right after the impact; at times after this the emission intensity is constant. All of these changes are discussed in terms of the photochemical mechanisms that have been thought to form the observed free radicals in comets. © 2009 Springer-Verlag Berlin Heidelberg.