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S.M. Larson (U. of Arizona), N. Samarasinha (NOAO), J. Tao (Shanghai Astron. Obs.), C. Hergenrother (U. of Arizona)
Digitally enhanced pre-perihelion groundbased images of Comet Hale-Bopp taken in September 1996 show intersting morphology resulting from at least two outbursts. During that apparition, the coma was dominated by radial ``porcupine" morphology. However, a 2 magnitude outburst starting on 1996 September 9.5 UT (Tao et al., 2000, Plan. Sp. Sci. 48, 153-161) resulted in two expanding dust shells with apparent expansion speeds of 112 and 225 m/s and an arc in the NW quadrant. This morphology is very similar to that seen in post-perihelion NICMOS images of a similar outburst on 1997 August 27 (see Campins et al., DPS 2000 abstract). Similar, but less pronounced outburst activity can be seen later in the month and include evidence for ejection of discrete fragments. We explore the possible mechanisms for the observed morphology.
This work is supported in part by the NASA Planetary Atmospheres Program.