Chapter 11.2: The Inner Planets


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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.

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Chapter 11.2: The Inner Planets

  1. 1. The Inner Planets Ch 11.2 (p382-387)
  2. 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.
  3. 3. 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
  4. 4. 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.
  5. 5. 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.
  6. 6. 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
  7. 7. 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
  8. 8. 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.
  9. 9. 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
  10. 10. Concept Check • How are the inner planets similar? • Why is Venus hotter than Mercury?
  11. 11. Earth • The third planet from the Sun • Unlike Mercury and Venus, Earth has a moon.
  12. 12. 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
  13. 13. 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
  14. 14. 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
  15. 15. Mar’s Atmosphere • 95% carbon dioxide • Temperatures: -125C – 20C • Dust storms that last for months
  16. 16. 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