In July 1994, a comet broke up into many pieces and then crashed into Jupiter over the course of many days. The comet was called Shoemaker-Levy 9. The largest pieces left scars on the face of Jupiter. Some of the scars were larger than the Earth.
The bruise was noticed by an amateur astronomer on Sunday, July 19. University of California, Berkeley, astronomer Paul Kalas took advantage of previously scheduled observing time on the Keck II telescope in Hawaii to image the blemish in the early morning hours of Monday, July 20
A large impact was observed with the Keck II telescope and its near-infrared camera at Mauna Kea on July 20 11:20 UT. It occurred on the surface of Jupiter.