EFFECT OF EOS ON BREAK-UP OF SHOEMAKER-LEVY-9 ENTERING JOVIAN ATMOSPHERE

Break-up of Comet Shoemaker-Levy 9 entering Jovian atmosphere was stud ied with highly accurate hydrocode EXCIPHER by changing the equation o f state (EOS) of the comet. The comet of radius 1.5 km was completely destroyed around the atmospheric pressure of 10 bar which is shallower than the result by Mac Low and Zahnle. Furthermore, the behavior of b reak-up is quite different from them. This behavior depends on the typ e of EOS. For hard material like water and ice, the impact of Jovian a tmosphere caused incompressible surface wave propagating along the com et surface thus enhancing ablation loss in low pressure atmosphere. Fo r ideal EOS, however, the surface wave did not appear since the comet was compressed upon impact and hence the ablation loss around 5 bar wa s quite low. Although the comet was broken into moderate pieces at 10 bar, most of the energy had already been lost well before the break-up . Surprisingly, however, the final disintegration occurred around 10 b ar for tested EOS and even for planar geometry.