This dramatic image was sent back to Earth from the Cassini space probe, currently on its way to Saturn. It passed Jupiter on the way and relayed back an excellent gallery of images.
One of the things we see in this image is Jupiter's famous Red Spot (lower left), an immense storm that has been brewing for at least 300 years. The small moon Io (lower right) is passing in front of Jupiter from the spacecraft's line of sight. These "transits" are common events among Jupiter's 4 large Galilean moons and can be seen from Earth through any size telescope. Io casts its shadow on the giant planet, seeming punching a hole in it!