 The comet had apparently passed extremely close to Jupiter on July 7 , 1992 , just over 40 @,@ 000 km ( 25 @,@ 000 mi ) above its cloud tops — a smaller distance than Jupiter 's radius of 70 @,@ 000 km ( 43 @,@ 000 mi ) , and well within the orbit of Jupiter 's innermost moon Metis and the planet 's Roche limit , inside which tidal forces are strong enough to disrupt a body held together only by gravity . Although the comet had approached Jupiter closely before , the July 7 encounter seemed to be by far the closest , and the fragmentation of the comet is thought to have occurred at this time . Each fragment of the comet was denoted by a letter of the alphabet , from " fragment A " through to " fragment W " , a practice already established from previously observed broken @-@ up comets . 
