CAN THE SODIUM TAIL OF COMET HALE-BOPP HAVE A DUST-IMPACT ORIGIN

Consideration is given to the possible mechanisms responsible for the production of the atomic sodium tail of comet Hale-Bopp. It is shown t hat both photosputtering and ion sputtering of nonvolatile dust grains might not be the main driving force. Instead, the generation of impac t vapor by collisional interaction between the cometary dust coma of m icron-sized particles and the very small grains (VSGs) of 10-100 Angst rom size could possibly account for the observations if a large amount of VSGs existed in the coma region.