Why did the comet break apart?
The comet broke apart due to tidal forces on its closest approach to Jupiter (perijove) on July 7, 1992 when it passed within the theoretical Roche limit of Jupiter. Shoemaker-Levy 9 is not the first comet observed to break apart. Comet West shattered in 1976 near the Sun [3]. Astronomers believe that in 1886 Comet Brooks 2 was ripped apart by tidal forces near Jupiter [2]. Several other comets have also been observed to have split [41]. Furthermore, images of Callisto and Ganymede show crater chains which may have resulted from the impact of a shattered comet similar to Shoemaker- Levy 9 [3,17]. The satellite with the best example of aligned craters is Callisto with 13 crater chains. There are three crater chains on Ganymede. These were first thought to be from basin ejecta; in other words secondary craters [27]. See SEDS.LPL.Arizona.edu in /pub/astro/SL9/images for images of crater chains (gipul.gif and chain.gif). There are also a few examples of crater chains on our Moon. Jay Melos
