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

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