Comet Shoemaker–Levy 9 were observed, with the largest coming on July 18 at 07:33 UTC when fragment G struck Jupiter. This impact created a giant dark spot over across, and was estimated to have released an energy equivalent to 6,000,000 megatons of TNT (600 times the world's nuclear arsenal). Two impacts 12 hours apart on July 19 created impact marks of similar size to that caused by fragment G, and impacts continued until July 22, when fragment W struck the planet. Observers hoped that the impacts would give them a first glimpse of Jupiter beneath the cloud tops, as lower material was exposed
Comet Shoemaker–Levy 9 Despite published predictions, astronomers had not expected to see the fireballs from the impacts and did not have any idea in advance how visible the other atmospheric effects of the impacts would be from Earth. Observers soon saw a huge dark spot after the first impact. The spot was visible even in very small telescopes, and was about (one Earth radius) across. This and subsequent dark spots were thought to have been caused by debris from the impacts, and were markedly asymmetric, forming crescent shapes in front of the direction of impact. Over the next six days, 21 distinct impacts