The thin ring in the above photo is possibly a shock wave in the atmosphere moving outward from where the fragment exploded below the cloud-tops. The dark semi-circles south of the impact points are probably an ejecta blanket composed of fine material condensed from the plume. This material is either from the comet itself, or from Jupiter, and is suspended in the upper atmosphere.
Some scientists refer to the dark material as soot, silicates, or tar-like hydrocarbons.
In the infrared they look bright because of relected sunlight, and in the visible spectral region they are generally darker than the Jovian clouds. E. Shoemaker believes G's kinetic energy was equivalent to 6 trillion tons TNT, hundreds of times greater than the world's entire nuclear arsenal. If it struck the Earth instead, it would have left a crater 60 km across. No trace of water was detected. Press HERE to FTP a binhexed, self-extracting Macintosh copy in DocMaker format.