NASA and STScI
Astronomers witnessed a rare event in 1994 when they watched the
shattered comet Shoemaker-Levy 9 smash into Jupiter piece by piece.
(An image of the comet fragments, shown in the inset above, was taken
as they approached the planet.) This was the first time that scientists
knew in advance where to view the collision of two bodies in space.
The comet pieces left a line of dark smudges (visible in the photo)
after hitting Jupiter's upper atmosphere.