Release of C₂ Radicals after the Deep Impact Event

Abstract

We present the results of investigating the coma of comet 9P/Tempel 1 in C₂ and continuum, before and after the Deep Impact event of 4 July 2005. A jet-like coma feature was produced by the impact, and its temporal evolution in morphology and brightness has been compared for the dust and gas coma. It shows that the feature remains visible in the dust coma for several days, whereas in the C₂ coma it is visible only on the image taken 15.8 hours after the impact and has vanished when the coma was observed again in the following night. The observational evidence strongly supports that the C₂ in the feature observed on 4 July 2005 was produced from fresh dust particles released by the outburst and forming an extended source for the production of the C₂ radical. This indicates that the disintegration of C₂-bearing dust species can directly be observed during the non-steady state conditions present immediately after outbursts and/or nucleus splitting.