Calculations showed that its unusual broken up form was due to a previous closer approach to Jupiter in July 1992. At that time, the orbit of Shoemaker-Levy 9 passed within Jupiter's Roche limit. Jupiter's tidal forces had acted to pull the comet apart. The comet was later observed as a series of pieces up to in diameter. These fragments collided with Jupiter's southern hemisphere between July 16 and July 22, 1994. The pieces were moving at a speed of approximately 60 km/s. The impact scars were more easily seen than the Great Red Spot and they stayed for many months.