EXPLOSION OF COMET SHOEMAKER-LEVY-9 ON ENTRY INTO THE JOVIAN ATMOSPHERE

We use the astrophysical hydrocode ZEUS to compute high-resolution mod els of the disruption and deceleration of cometary fragments striking Jupiter. We find that simple analytic and semianalytic models work wel l for kilometer-size impactors. We show that previous numerical models that placed the explosion much deeper in the atmosphere failed to ful ly resolve important gasdynamical instabilities. These instabilities t ear the comet apart, greatly increase its effective cross section, and bring it to an abrupt halt. A 1 km diameter fragment loses over 90% o f its kinetic energy within a single scale height at an atmospheric pr essure of order 10 bars. For all practical purposes, it explodes.