Near-Infrared Spectroscopy of the Shoemaker–Levy 9 Impact Sites with UKIRT: CO Emission from the L Site and Additional 5-μm Spectra

Abstract

CO emission lines in the 4.7-μm fundamental vibrational band were detected from Jupiter at the Shoemaker–Levy 9 fragment L impact site on July 20, 1994 UT, 4 to 5 hr after impact. For an atmospheric model with a single temperature for the emitting CO, which is assumed to be in local thermodynamic equilibrium (LTE), the CO temperature is estimated to beT(CO) = 280 ± 10 K. For this case, the CO column density isN(CO) = 1.2 × 1017cm−2and the estimated mass of CO in the L site is 1.6 × 1013g, with uncertainties of a factor five. The oxygen in this mass of CO can be plausibly explained as coming from material originally in the impactor. Larger amounts of cool CO below the emitting CO could have been present, however. The possible departure of the CO vibrational level populations from LTE and the effect on abundance estimates are discussed qualitatively. Spectra of other impact sites taken at times on the order of days after impact show no detectable changes in the CO absorption lines of impact sites vs nonimpact sites.