SPH Calculations of Comet Shoemaker-Levy-9/Jupiter Impact

Previous abstract Next abstract

Session 14 -- Comets, Asteroids, Meteoroids
Oral presentation, Monday, 30, 1994, 10:00-11:30

[14.01] SPH Calculations of Comet Shoemaker-Levy-9/Jupiter Impact

C.A.Wingate, N.M.Hoffman, R.F.Stellingwerf (LANL)

The impact of Comet Shoemaker-Levy 9 has been simulated in 2D axisymmetric geometry and full 3D using the Los Alamos Smooth Particle Hydrodynamics code (SPHINX). The objective of this study is to calculate energy deposition profiles and fireball evolution histories for a range of comet parameters. We hope to use these results to infer comet properties from observations. The modeling proceeds in two phases. In Phase I, the collision of the incoming fragment, or bolide, is calculated, and its kinetic energy profile is differentiated to give an energy deposition profile. The deposition profile is used as input to Phase II (see companion paper by Stellingwerf et al.) in which the fireball evolution is calculated.

Two different bolide densities were simulated, 0.2 $g/cm^{3}$ and 0.92 $g/cm^{3}$. The incoming bolide velocity was 60 km/sec and the impact angle was taken to be 45 degrees. Since the calculation is 2D, this means simply that the bolide's depth in the atmosphere is equal to its distance traveled times the cosine of 45 degrees. The baseline calculation assumed a spherical bolide with a diameter of 1 km. Various physical models were used for the bolide including perfect gas equations of state (eos), more realistic eos's and strength of materials.

The model for the Jupiter atmosphere was a fit to the Orton atmosphere. The eos for the atmosphere for most of the calculations was taken to be a perfect gas with a gamma of 1.2. A sesame tabular eos was also used. Rather than modeling the entire atmosphere, small sections were modeled using blocks of particles with blocks being shuffled in and out as the calculation progressed. Calculations were done with different size sections to test the sensitivity of the results to this procedure.

The results indicate energy deposition for the 0.2 density, 1 km diameter case occurring between 50-200 km. The penetration is seen to increase somewhat as the bolide resolution is improved.

Monday program listing