9.18: A Comet Impacts a Planet
Except for seeing meteors enter our atmosphere, no contemporary astronomer had ever observed an impact on another world until 1994. Comet Shoemaker–Levy 9, S-L 9, was discovered in March 1993 by astronomers Eugene and Carolyn Shoemaker and David Levy. Carolyn’s first impression of the discovery photo was it “looked like a squashed comet. ” This description was due to the fact that the comet had been broken apart by the gravitational pull of Jupiter. The largest cometary fragment was 2 kilometers or 1. 2 miles across.
After determining the comet’s orbit, it was found that Shoemaker–Levy 9 fragments would impact Jupiter over several days, 22-26 July 1994. The question became if the impacts would be visible to astronomers and orbiting satellites, like the Hubble Space Telescope.
Over the five-day period, twenty-one (21) distinct impacts were observed by satellites like the Hubble Space Telescope, as well as Earth-based telescopes. Fireballs resembling an atomic bomb mushroom cloud were seen at Jupiter’s horizon. Dark spots were seen in the upper atmosphere of Jupiter after impact; these were visible even in small amateur telescopes. Some of these spots were as big as Earth. The black impact features were visible on Jupiter for months; some likened them to a black eye. Due to the S-L 9 series of impacts, astronomers were better able to explain rows or chains of craters found on the Moon and other objects, like Jupiter’s moon Ganymede.