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Session 42 - Solar Systems.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center

[42.13] Re-entry Shock Temperatures of the R Fragment of Comet Shoemaker-Levy 9

S. J. Kim (Kyunghee U.), M. Ruiz, G. H. Rieke, M. J. Rieke (Steward Obs.), K. Zahnle (ARC), M. Mac Low (U. Chicago)

The R flare is unique among the 22 impacts on Jupiter of fragments of Comet Shoemaker-Levy 9 (SL9) because it was intensely observed from various groundbased observatories as well as with the Galileo spacecraft. However, it has been difficult to deduce a coherent picture of the temperatures, constituents, and physical characteristics of the R flare from lightcurves derived from imaging data or low-resolution spectra. Here we present a time series of high resolution near-IR spectra which show strong CO emission. We obtained the near-IR spectra of the flash in the 2.28 - 2.36 micron range with a temporal resolution of 50 seconds at the Steward Observatory 2.3-m telescope on July 20, 1994. The primary instrument was FSPEC, a cryogenic, long slit IR spectrometer using a 256 x 256 NICMOS3 array with a spectral resolving power of approximately 3600. The derived rotational temperature of the CO was 1500 K or less at the beginning of the flare and it increased steadily to at least 5000 K at the end, by which time the flare had faded away. The increasing CO temperature is consistent with a ballistic plume model, in which ejecta launched on the highest trajectories were the last to fall, with the CO recording the temperature of the shock where the plume reentered the jovian atmosphere. This process is broadly analogous to the suggestion that returning ejecta from the K/T impactor released huge amounts of energy in the earth's upper atmosphere, leading to mass extinctions.

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