What I would like to discuss here is the chemical nature of the nucleus.

This implies the consideration of the vaporization of the nucleus into the coma because the coma is our only source of information on the nucleus. The nature of the parent molecules vaporizing from the nucleus has been for a long time the missing link for our understanding of the molecular processes. A major development has been brought about by the first identification of three neutral parent molecules HCN and CH3 CN identified in Comet Kohoutek, H20 in Comet Bradfield, confirmed by H2O+ in Kohoutek.