When Comet Shoemaker Levy 9 impacted Jupiter in July 1994 there was so many different versions of what the impact would be, from nothing happening to large spots.
I was in the camp of nothing happening at all due to the size of Jupiter and the minuscule size of the Comet fragments
As it was it turned out to be beyond most peoples imagination and was one of the most memorable sights in my time doing Astronomy
That this impact didn't live up to peoples expectations just goes to show that nothing is certain in when it comes to doing experiments of this kind.
They may get lots of science out of the mission but unfortunately not much in the visible for us interested amateur astronomers and the general public