THERMAL INFRARED IMAGING SPECTROSCOPY OF SHOEMAKER-LEVY-9 IMPACT SITES - TEMPERATURE AND HCN RETRIEVALS

We present high-resolution 8-14 mu m observations of Shoemaker-levy 9 sites conducted on July 20, 30, and 31 1994 UT at the NASA Infrared Te lescope Facility. Stratospheric heating was detected from strong enhan cements of methane emission near 8.1 mu m over areas at least 15,000 k m wide around the K site observed 23 hr after impact and around the L site 11 hr after impact. The intensity distribution between strong and weaker CH4 lines implies that the stratospheric heating was primarily confined to pressures less than 500 mu bar. The L site temperature in creased by 80 +/- 10 K at 5 mu bar, but did not exceed 20 K around 1 m bar or 10 K around 10 mbar. The older K site was still 30 +/- 5 K warm er than the surroundings at the 10-mu bar level. The excess thermal en ergy stored in the upper jovian stratosphere was 3(-1.5)(+3) x 10(26) erg over the L site, and 2(-1)(+2) x 10(26) erg over the K site at the time of the observations. Comparison with numerical simulations indic ates that a large fraction (>20%) of the kinetic energy of the L plume was transferred to the jovian atmosphere and not immediately radiated away. Acetylene line emission near 13.4 mu m was enhanced over an are a similar to 18,000 km wide centered on the E site 2.6 days after impa ct. Radiative transfer models of this emission indicate temperatures 3 7 +/- 7 K higher than nominal around 3 mu bar. No such enhancement was seen in CH, spectral images, implying that the temperature perturbati on did not significantly extend below the similar to 20-mu bar level. The H site observed simultaneously was 12 +/- 5 K warmer than the surr oundings 1.4 day after impact. C2H2 lines were still slightly more int ense over the K + W and Q1 sites on July 30 and 31, 8 to 10 days after impact. These observations can be interpreted either by temperature d ifferences of about 13 and 10 K respectively in the 3-mu bar region, o r by an increase in the C2H2 column density of 2.5-5 x 10(17) molecule cm(-2). Emission from hydrogen cyanide lines around 13.4 mu m was det ected over all sites observed, The mass of HCN is about 2 x 10(12) g f or the biggest plumes (K, L, G), 0.95 +/- 0.5 x 10(12) g over the E si te, and 0.45 +/- 0.2 x 10(12) g over the H site, The total mass of HCN produced by all fragments is estimated to be 1.1 +/- 0.4 x 10(13) g. A consistent interpretation of the different pieces of information ava ilable suggests that the H plume was richer in dust than the E or A pl ume. (C) 1997 Academic Press