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Planets of the Solar System
Section 3
Key Ideas
• Identify the basic characteristics of the inner planets.
• Compare the characteristics of the inner planets.
• Summarize the features that allow Earth to sustain life.
of the rings of Saturn with the rings of the other outer
planets.
Planets of the Solar System
Section 3
The Inner Planets
• ____________, ___________, __________, and _______
are the planets closest to the sun and are called the
________ planets or _____________ planets.
• _____________ planets one of the highly dense planets
nearest to the sun; Mercury, Venus, Mars, and Earth
• These planets consist mostly of solid _______and metallic
cores. The number of moons per planet varies from
_______ to _________.
• The surfaces of inner planets have bowl-shaped
depressions called __________ __________, that were
caused by _____________ of the planets with other objects
in space.
Planets of the Solar System
Section 3
Mercury
• Mercury, the planet closest to the sun, circles the sun every
______ days. Mercury rotates on its axis once every
______ days.
• Ancient Romans named the planet after the ____________
of the gods, who moved very quickly.
• Mercury’s surface is heavily _____________.
• The absence of a significant _______________ and the
planet’s slow ___________ contribute to the large daily
temperature range on Mercury.
• The temperature may reach as high as ______°C during
the day and plunge to ______°C at night.
Planets of the Solar System
Section 3
Venus
• Venus is the second planet from the sun and has an orbital period of
_______ days.
• Venus rotates very slowly, only once every ______ days.
• Venus and Earth are of almost the same _______, ________, and
____________, but differ greatly in other areas.
Venus’s Atmosphere
• Venus’s atmospheric pressure is about _____ times the pressure on
Earth.
• Venus’s atmosphere is about 96% _________. The high
concentration of carbon dioxide in the atmosphere blocks most of
the ____________ radiation from escaping. This type of heating
known as the _______________ effect.
Planets of the Solar System
Section 3
Venus, continued
Venus’s Atmosphere, continued
• The greenhouse effect on Venus makes the average surface
temperature ______°C, a phenomenon commonly referred to as a
____________ greenhouse effect.
• Sulfur dioxide droplets in Venus’s upper atmosphere form a cloud
layer that __________ sunlight. The cloud layer reflects the sunlight
so strongly that, from Earth, Venus appears to be the ___________
object in the night sky, aside from Earth’s ________ and ______.
• Because Venus appears near the sun, Venus is usually visible from
Earth only in the ___________________________. Therefore,
Venus is commonly called the _________ star or the __________
star.
Planets of the Solar System
Section 3
Venus, continued
Missions to Venus
• In the 1970s, the _______ _________ sent six probes to
explore the surface of Venus.
• The probes transmitted surface images of a rocky
landscape, a smooth plain, and some rocks.
• Other instruments indicated that the surface of Venus is
composed of ________ and _________.
• In the 1990s, the United States’s ____________ satellite
collected atmospheric data and bounced radio waves off
Venus to produce radar images of Venus’s surface.
Planets of the Solar System
Section 3
Venus, continued
Surface Features of Venus
• Scientists discovered landforms such as ____________,
_____________, _______________, and ________ dunes.
• _______________ and lava plains are the most common features
on Venus. Maat Mons is Venus’s highest volcano, at an elevation of
____ km.
• The surface of Venus is also somewhat cratered. All the craters are
about the same age, and they are surprisingly young.
• Scientists speculate that Venus’s surface undergoes periodic
______________ as a result of massive volcanic activity.
Planets of the Solar System
Reading check
How is Venus different from Earth?
Section 3
Planets of the Solar System
Section 3
Earth
• Earth is the ________ planet from the sun.
• The orbital period of Earth is __________ days, and
Earth completes one rotation on its axis every ______.
• Earth has one large __________.
• Geologic records indicate that over the last ______
million years, Earth’s surface has undergone many
changes.
Planets of the Solar System
Section 3
Earth, continued
Water on Earth
• Earth’s unique ______________ and __________ from the
sun allow water to exist in a liquid state.
• Other planets are too close or far away from the sun, so that
liquid water _______ or ___________.
Life on Earth
• Earth is the only known planet that has the proper
combination of ________, _____________, and _________to
support life.
Planets of the Solar System
Section 3
Mars
• Mars is the fourth planet from the sun, about _____%
farther from the sun than Earth is.
• Its orbital period is _______ days, and it rotates on its
axis every ____ hours and ____ minutes.
• Mars’s _____________ are much like Earth’s seasons
because its axis tilts at nearly the same angle that Earth
does.
Planets of the Solar System
Section 3
Mars, continued
Martian Volcanoes
• Tharsis Montes is one of several volcanic regions on Mars.
• The largest volcano on Mars is Olympus Mons, which is nearly
_____ km tall. It is three times as tall as Mount Everest. The base of
Olympus Mons is 550 km across, about the size of _____________.
• Scientists think that the volcano has grown so large because Mars
has no moving ____________ ___________.
• A Viking landing craft detected two geological events that produced
seismic waves, called ______________, which may indicate that
volcanoes on Mars are __________.
Planets of the Solar System
Section 3
Reading check
Why are Martian volcanoes larger than Earth’s volcanoes?
Planets of the Solar System
Section 3
Mars, continued
Water on Mars
• The pressure and temperature of Mars’s atmosphere are
too _______ for water to exist as a liquid on Mars’s
surface.
• Several NASA spacecrafts have found evidence that
liquid water did exist on Mars’s surface in the past.
Surface features on Mars are characteristic of
_________ by water.
• Although most of the water on Mars is trapped in polar
_________, water also exists as ______ just below the
surface.