Jupiter
Dana Desonie, Ph.D.
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Printed: May 13, 2013
AUTHOR
Dana Desonie, Ph.D.
www.ck12.org
C ONCEPT
Concept 1. Jupiter
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Jupiter
• Describe the characteristics of Jupiter.
What are Jupiter’s most distinctive features?
Jupiter has been well studied for being so far away. Many flybys, one orbiter, and a probe have all visited the planet.
While the possibility exists for humans to reach Mars, a manned trip to Jupiter seems a long ways away. The round
trip would take at least 10 years. Who would want to spend more than a decade on a spaceship? At least they could
see the Great Red Spot and other features in person!
Jupiter
Jupiter is the largest planet in our solar system. Jupiter is named for the king of the gods in Roman mythology. The
Romans named the largest planet for their most important god. They followed the tradition of the Greeks, who had
similarly named the planet Zeus. The Romans built a temple to Jupiter on the hill.
Jupiter is truly a giant! The planet has 318 times the mass of Earth, and over 1,300 times Earth’s volume. So Jupiter
is much less dense than Earth. Because Jupiter is so large, it reflects a lot of sunlight. When it is visible, it is the
brightest object in the night sky besides the Moon and Venus. Jupiter is quite far from Earth. The planet is more
than five times as far from Earth as the Sun. It takes Jupiter about 12 Earth years to orbit once around the Sun.
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A Ball of Gas and Liquid
Since Jupiter is a gas giant, could a spacecraft land on its surface? The answer is no. 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, the intense pressure condenses the gases into a liquid. Jupiter may have
a small rocky core at its center.
A Stormy Atmosphere
Jupiter’s atmosphere is unlike any other in the solar system! The upper layer contains clouds of ammonia. The
ammonia is different colored bands. These bands rotate around the planet. The ammonia also swirls around in
tremendous storms. The Great Red Spot, shown in Figure 1.1, is Jupiter’s most noticeable feature. The spot is an
enormous, oval-shaped storm. It is more than three times as wide as the entire Earth! Clouds in the storm rotate
counterclockwise. They make one complete turn every six days or so. The Great Red Spot has been on Jupiter for
at least 300 years. It may have been observed as early as 1664. It is possible that this storm is a permanent feature
on Jupiter. No one knows for sure.
FIGURE 1.1
The Great Red Spot has been on Jupiter
since we’ve had telescopes powerful
enough to see it.
Moons and Rings
Jupiter has lots of moons. As of 2012, we have discovered over 66 natural satellites of Jupiter. Four are big enough
and bright enough to be seen from Earth using a pair of binoculars. These four moons were first discovered by
Galileo in 1610. They are called the Galilean moons. Figure 1.2 shows the four Galilean moons and their sizes
relative to each other. These moons are named Io, Europa, Ganymede, and Callisto. The Galilean moons are larger
than even the biggest dwarf planets, Pluto and Eris. Ganymede is the biggest moon in the solar system. It is even
larger than the planet Mercury!
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Concept 1. Jupiter
FIGURE 1.2
The Galilean moons are as large as small planets.
Scientists think that Europa is a good place to look for extraterrestrial life. Europa is the smallest of the Galilean
moons. The moon’s surface is a smooth layer of ice. Scientists think that the ice may sit on top of an ocean of liquid
water. How could Europa have liquid water when it is so far from the Sun? Europa is heated by Jupiter. Jupiter’s
tidal forces are so great that they stretch and squash its moon. This could produce enough heat for there to be liquid
water. Numerous missions have been planned to explore Europa, including plans to drill through the ice and send a
probe into the ocean. However, no such mission has yet been attempted.
Photos from the Voyager missions showed that Jupiter has a ring system. This ring system is very faint, so it is very
difficult to observe from Earth.
Exploration
Jupiter has fascinated scientists at least since Galileo turned his first telescope on the planet. In 1979, two spacecrafts,
Voyager 1 and Voyager 2, visited Jupiter and its moons. The Galileo orbiter orbited the planet for seven years and
flew by all of the Galilean moons plus one other moon. The orbiter released a probe to study the planet’s atmosphere.
Future missions to Jupiter are underway. Juno will arrive in late 2016.
Vocabulary
• Galilean moons: The four largest moons of Jupiter discovered by Galileo: Io, Europa, Ganymede and Callisto.
• Great Red Spot: An enormous, oval-shaped, long-lived storm on Jupiter.
Summary
• Jupiter is mostly hydrogen with some helium, and may contain a small rocky core.
• Jupiter has a thick atmosphere. The Great Red Spot is a storm that has been going for at least 300 years.
• One of Jupiter’s moons, Europa, appears to have a liquid ocean beneath the surface. This ocean could be a
place for life.
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Practice
Use this resource to answer the questions that follow.
The Planet Jupiter at http://www.youtube.com/watch?v=KcGCJwcmx2o (8:08)
MEDIA
Click image to the left for more content.
1.
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10.
How does the mass of Jupiter compare to Earth?
How quickly does it rotate on its axis?
What makes the different bands on the planet?
What is happening to the Giant Red Spot?
What two elements make up the majority of Jupiter?
What happened to the Comet Shoemaker-Levy 9?
How many moons does Jupiter have?
What is unique about Ganymede?
Describe Jupiter’s ring system.
What causes the auroras on Jupiter?
Review
1. Why is the Great Red Spot thought to be a storm? How could scientists know that it’s been going on for at
least 300 years?
2. What is Jupiter made of?
3. Why do scientists think that Europa could have life?
References
1. Courtesy NASA. . Public Domain
2. Courtesy NASA/JPL-Caltech. . Public Domain
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