Numerical modeling of the disruption of comet D/1993 F2 shoemaker-levy 9 representing the progenitor by a gravitationally bound assemblage of randomly shaped polyhedra

We advance the modeling of rubble-pile solid bodies by re-examining the tidal breakup of comet ShoemakerLevy 9, an event that occurred during a 1.33 R₄ encounter with Jupiter in 1992 July. Tidal disruption of the comet nucleus led to a chain of sub-nuclei ∼1001000 m diameter; these went on to collide with the planet two years later. They were intensively studied prior to and during the collisions, making SL9 the best natural benchmark for physical models of small-body disruption. For the first time in the study of this event, we use numerical codes treating rubble piles as collections of polyhedra. This introduces forces of dilatation and friction, and inelastic response. As in our previous studies we conclude that the progenitor must have been a rubble pile, and we obtain approximately the same pre-breakup diameter (∼1.5 km) in our best fits to the data. We find that the inclusion of realistic fragment shapes leads to grain locking and dilatancy, so that even in the absence of friction or other dissipation we find that disruption is overall more difficult than in our spheres-based simulations. We constrain the comets bulk density at ρbulk ∼300400 kg m^-3, half that of our spheres-based predictions and consistent with recent estimates derived from spacecraft observations.