Originally Posted by Michael Mozina

Actually the composition of Saturn and Jupiter aren't well understood, and these statements are based on gas model "predictions", not direct observation. If you could point me to spectral data on the Shoemaker-Levi 9 explosion, I'll bet well find plenty of heavy elements, both from the comet and Jupiter itself. That comet hit something that was VERY dense indeed, and at not a very great depth either.