Comet Shoemaker–Levy 9 chains on the Jovian moons did not lead back to a larger crater. The impact of SL9 strongly implied that the chains were due to trains of disrupted cometary fragments crashing into the satellites. On July 19, 2009, exactly 15 years after the SL9 impacts, a new black spot about the size of the Pacific Ocean appeared in Jupiter's southern hemisphere. Thermal infrared measurements showed the impact site was warm and spectroscopic analysis detected the production of excess hot ammonia and silica-rich dust in the upper regions of Jupiter's atmosphere. Scientists have concluded that another impact event had occurred, but
Naming of comets the past, when multiple comets were discovered by the same individual, group of individuals, or team, the comets' names were distinguished by adding a numeral to the discoverers' names (but only for periodic comets); thus Comets Shoemaker–Levy 1 to 9 (discovered by Carolyn Shoemaker, Eugene Shoemaker & David Levy). Today, the large numbers of comets discovered by some instruments makes this system impractical, and no attempt is made to ensure that each comet is given a unique name. Instead, the comets' systematic designations are used to avoid confusion. Until 1994, comets were first given a provisional designation consisting of the