INFRARED SPECTRUM FROM THE PLUME OF THE SL9 H-IMPACT ON JUPITER

These two graphs show the infrared emission in the 3.50 - 3.56 micron
spectral band, as observed from the plume over the area where fragment
H impacted on Jupiter.  This violent event took place on July 18, at
about 19:32 UT.  The spectra were obtained with the IRSPEC spectrograph
attached to the Nasmyth focus to the ESO 3.5-metre New Technology
Telescope.  They were obtained simultaneously at 19:50 UT, or about 18
minutes after the impact, and less than 15 minutes after the bright 
plume became visible at the limb.  The exposure time was 1 minute and
the observers were Therese Encrenaz (Observatoire de Paris-Meudon, 
France), Rita Schulz adn Joachim A. Stuewe (Max-Planck-Institut fuer 
Astronomie, Katlenburg-Lindau, Germany) and Guenther Wiedemann (ESO).

The first spectrum shows the emission of methane (CH4) observed near
the center of the H impact region.  These S-emission bands are usually
not observed in Jupiter, but are present in this spectrum because of 
the high temperature (T = 700 K) that is a result of the large amount
of energy deposited by the violent impact.

The second spectrum shows the same band of methane in the same IRSPEC
spectrum, but now as observed at the leading side of the H impact
region.  The change in the slope is due to a very high rotational 
temperature (several thousand degrees).  Such a high temperature was
not expected such a long time after the impact.  Many new unidentified
lines appear in the spectrum; some of them might be due to other bands
of methane.

This is ESO PR Photo SL9J/94-17.  It may be reproduced, if credit is
given to the European Southern Observatory.