A Ball of Gas and Liquid
If a spaceship were to try to land on the surface of Jupiter, the astronauts would find that
there is no solid surface at all! Jupiter is made mostly of hydrogen, with some helium, and
small amounts of other elements. The outer layers of the planet are gas. Deeper within the
planet, pressure compresses the gases into a liquid. Some evidence suggests that Jupiter may
have a small rocky core at its center.
A Stormy Atmosphere
The upper layer of Jupiter’s atmosphere contains clouds of ammonia (NH 3 ) in bands of
different colors. These bands rotate around the planet, but also swirl around in turbulent
storms. TheGreat Red Spot,shown inFigure25.21, is an enormous, oval-shaped storm
found south of Jupiter’s equator. It is more than three times as wide as the entire Earth!
Clouds in the storm rotate in a counterclockwise direction, making one complete turn every
six days or so. The Great Red Spot has been on Jupiter for at least 300 years. It is possible,
but not certain, that this storm is a permanent feature on Jupiter.
Figure 25.21: This image of Jupiter’s Great Red Spot (upper right of image) was taken by
the Voyager 1 spacecraft. The white storm just below the Great Red Spot is about the same
diameter as Earth. ( 7 )