s8pe-41302-ca
10/28/05
12:36 PM
MAZER
Page 419
KEY CONCEPT
The inner solar system
has rocky planets.
CALIFORNIA
Content Standards
8.2.g Students know
the role of gravity in
forming and maintaining the shapes of
planets, stars, and the
solar system.
8.4.e Students know
the appearance,
general composition,
relative position and
size, and motion of
objects in the solar
system, including
planets, planetary
satellites, comets,
and asteroids.
BEFORE, you learned
NOW, you will learn
• Planets are closer together in
the inner solar system than in
the outer solar system
• Planets formed along with
the Sun
• Gravity made planets round
• How four processes change the
surfaces of solid planets
• How atmospheres form and
then affect planets
• What the planets closest
to the Sun are like
EXPLORE Surfaces (8.4.e)
How does a planet’s mantle affect its surface?
MATERIALS
PROCEDURE
1
Dampen a paper towel and place it on top
of two blocks to model a crust and a mantle.
• 2 blocks
• paper towel
• newspaper
2 Move one block. Try different amounts
of motion and different directions.
VOCABULARY
terrestrial planet p. 419
tectonics p. 420
volcanism p. 420
WHAT DO YOU THINK?
• What happened to the paper towel?
• What landforms like this have you seen?
The terrestrial planets have rocky crusts.
Scientists study Earth to learn about other planets. They also study
other planets to learn more about Earth. The terrestrial planets are
Mercury, Venus, Earth, and Mars—the four planets closest to the Sun.
They all have rocky crusts and dense mantles and cores. Their insides,
surfaces, and atmospheres formed in similar ways and follow similar
patterns. One planet—Earth—can be used as a model to understand the others. In fact, the term terrestrial comes from terra,
the Latin word for Earth.
Earth
Most of Earth’s rocky surface is hidden by water. More details about Earth
and other planets are listed in the Appendix at the back of this book.
Mass 6 1024 kg
Diameter 12,800 km
Average distance from Sun 1 AU
Orbits in 365 days
Rotates in 24 hours
Chapter 13: Our Solar System 419
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