Comet Shoemaker-Levy impact on Jupiter, July 1994. First in a series of five frames from a computer simulation, showing the effect of the impact of a 1-km diameter comet on the atmosphere of Jupiter. The altitude scale in the model is exaggerated, giving the atmosphere a 'lumpy' appearance. This frame shows Day 0, just before the impact occurs. Over 20 1-km or larger fragments from Comet Shoemaker-Levy 9 are due to hit Jupiter on 18-24 July 1994. The comet was broken up by Jupiter's gravity during a close encounter in July 1992.