JOVIAN SOOT FROM COMETARY IMPACTS

It seems to be widely accepted that the dark spots on Jupiter caused b y the impacting fragments of comet Shoemaker-Levy 9 are due to dust pa rticles which have formed immediately after the impacts. However, the actual nature and origin of these grains is still uncertain. We propos e that they may consist of amorphous carbon and have calculated the ti me-dependent formation and growth of such dust particles assuming an e xponential pressure decrease in an adiabatic fireball. The resulting p roperties of the grains, e.g. their sizes, are consistent with observa tions, The question whether carbon or silicate grains will form depend s critically on the chemical composition of the Jovian atmosphere. If a carbon-rich environment exists at the impact sites our model demonst rates that there is enough time to grow amorphous carbon grains in the fireballs rising immediately after the impacts.