Grade 8 Integrated Science Chapter 11 Lesson 2 on the inner planets. Discusses the four inner planets, their atmosphere, interior, surface, weather, and other defining features. Includes individual slides on Mercury, Venus, Earth and Mars.

1. The Inner Planets
Ch 11.2 (p382-387)

2. Planets Made of Rock
• The inner planets – Mercury, Venus,
Earth, Mars – are also called terrestrial
planets.
• Terrestrial planets are the planets closet to
the Sun, are made of rock and metal, and
have solid outer layers.

4. Mercury
• The smallest planet
• Closest to the Sun
• No atmosphere
– The strength of a planet’s gravity depends on the
planet’s mass. Because Mercury’s mass is so small,
its gravity is not strong enough to hold onto an
atmosphere
• No atmosphere = no wind
– Temperatures:
• -170C on the side facing away from the Sun
• 450 C on the side facing the Sun

5. Mercury’s Surface
• Impact craters, depressions formed by collisions with
objects from space, cover the surface of Mercury.
• There are smooth plains of solidified lava from long-ago
eruptions.
• There are also high cliffs that might have formed when
the planet cooled quickly
• Without an atmosphere, almost no erosion occurs on
Mercury’s surface
– As a result, features that formed billions of years ago have
changed very little.

6. Mercury’s Surface
• Like all inner planets, Mercury has a core made
of iron and nickel.
• Surrounding the core is a layer called the
mantle.
• The mantle is mainly made of silicon and
oxygen.
• The crust is a thin, rocky layer above the mantle.
• Mercury’s large core might have been formed by
a collision with a large object during Mercury’s
formation.

8. Venus
• 2nd
planet from the Sun
• About the same size as Earth
• It rotates so slowly that its period of
rotation is longer than its period of
revolution.
– One day is longer than one year
• Venus rotates east to west, unlike most
planets

9. Venus’s Atmosphere
• The atmosphere of Venus is about 97%
carbon dioxide
• It is so dense that the atmospheric
pressure on Venus is about 90 times
greater than on Earth
• Venus has no water on its surface.
• It is covered by a thick layer of clouds
made of acid

10. The Greenhouse Effect on
Venus
• With an average temperature of about 460C,
Venus is the hottest planet in our solar system.
• The high temperature are caused by the
greenhouse effect
– The greenhouse effect occurs when a planet’s
atmosphere traps solar energy and causes the
surface temperature to increase.
• Without the greenhouse effect Venus would be
about 450C cooler.

11. Venus’s Structure and Surface
• Venus’s internal structure is similar to
Earth’s.
• Radar images show that more than 80%
of Venus’s surface is covered by solidified
lava

13. Concept Check
• How are the inner planets similar?
• Why is Venus hotter than Mercury?

14. Earth
• The third planet from the Sun
• Unlike Mercury and Venus, Earth has a
moon.

15. Earth’s Atmosphere
• A mixture of gases and a small amount of water
vapor make up most of Earth’s atmosphere
• They produce a greenhouse effect that
increases Earth’s average surface temperature
• This effect and Earth’s distance from the Sun
warm Earth enough for large bodies of water to
exist.
• Earth’s protective atmosphere, the presence of
liquid water, and the planet’s moderate
temperature range support a variety of life

16. Earth’s Structure
• Earth has a solid inner core surrounded by
a liquid outer core
• The mantle surrounds the liquid outer
core.
• Above the mantle is Earth’s crust.
• It’s broken into large pieces, called plates,
that constantly slide past, away from, or
into each other

18. Mars
• 4th
planet from the Sun
• Half the size of Earth
• Two very small and irregularly shaped
moons
• Water on Mars is mainly trapped in the
polar ice caps and a small amount in
found as liquid vapor
• However, little evidence of liquid water or
life has been found

19. Mar’s Atmosphere
• 95% carbon dioxide
• Temperatures: -125C – 20C
• Dust storms that last for months

20. Mar’s Surface
• Reddish due to iron oxide in the soil (rust)
• Enormous canyons
• Largest mountain in the solar system
• Polar ice caps made of frozen carbon
dioxide and ice