Comet Shoemaker–Levy 9 probably destroyed before they even reached the cloud layer. The visible scars from the impacts could be seen on Jupiter for many months. They were extremely prominent, and observers described them as even more easily visible than the Great Red Spot. A search of historical observations revealed that the spots were probably the most prominent transient features ever seen on the planet, and that although the Great Red Spot is notable for its striking color, no spots of the size and darkness of those caused by the SL9 impacts have ever been recorded before. Spectroscopic observers found that ammonia and
Comet Shoemaker–Levy 9 thus a serendipitous discovery, but one that quickly overshadowed the results from their main observing program. Comet Shoemaker–Levy 9 was the ninth periodic comet (a comet whose orbital period is 200 years or less) discovered by the Shoemakers and Levy, hence its name. It was their eleventh comet discovery overall including their discovery of two non-periodic comets, which use a different nomenclature. The discovery was announced in IAU Circular 5725 on March 27, 1993. The discovery image gave the first hint that comet Shoemaker–Levy 9 was an unusual comet, as it appeared to show multiple nuclei in an elongated region