The Inner Planets (pages )

Transcription

1 The Inner Planets (pages ) Introduction (page 712) Key Concept: The four inner planets are small and dense and have rocky surfaces. The four planets closest to the sun are called the inner planets. The four inner planets are Mercury, Venus, Earth, and Mars. The inner planets are called the terrestrial planets. The inner planets are more like one another than they are like the five outer planets. For example, the inner planets all have rocky surfaces. 1. The inner planets are called the planets. 2. Circle the letter of how many inner planets there are. a. 2 b. 4 c. 6 Earth (pages ) Key Concept: Earth is unique in our solar system in having liquid water at its surface. Earth has three main layers. The surface layer is the crust. Below the crust is the mantle. At Earth s center is the core. 337

2 Most of Earth s surface about 70 percent is covered with water. Earth is the only planet with liquid water on its surface. Earth s gravity holds onto most gases. The gases around Earth make up Earth s atmosphere. ideas on page 337 and above. 3. Is the following sentence true or false? Most of Earth s surface is covered with water. 4. Read each word in the box. Then fill in each blank in the picture below with one of the words. mantle crust core a. b. c. 338

3 Mercury (page 714) Key Concept: Mercury is the smallest terrestrial planet and the planet closest to the sun. Mercury is the closest planet to the sun. Mercury is the smallest of the inner planets. It is not much larger than Earth s moon. Mercury has almost no atmosphere because it has very weak gravity. Mercury has extreme temperatures on its surface. It is very hot during the day and very cold at night. 5. Circle the letter of each sentence that is true about Mercury. a. It is the closest planet to the sun. b. It has a very thick atmosphere. c. It is the smallest of the inner planets. 6. The picture shows the sun and the inner planets. Circle the planet Mercury. Sun 339

4 Venus (pages ) Key Concept: Venus s density and internal structure are similar to Earth s. But, in other ways, Venus and Earth are very different. Venus is very much like Earth in size and mass. Venus s atmosphere is very thick. It is always cloudy on Venus. Venus has the hottest surface of any planet. Venus s atmosphere traps the sun s heat. The trapping of heat by the atmosphere is called the greenhouse effect. 7. Circle the letter of each sentence that is true about Venus. a. It is much larger than Earth b. It has a very thick atmosphere. c. It has no clouds in its atmosphere. 8. The trapping of by Venus s atmosphere is called the greenhouse effect. 9. Is the following sentence true or false? Venus has the hottest surface of any planet. 340

5 Mars (pages ) Key Concept: Scientists think that a large amount of liquid water flowed on Mars s surface in the distant past. Mars is called the red planet because it looks red from Earth. The surface of Mars has huge canyons and ancient coastlines. Scientists think that liquid water may have formed these features. There is no liquid water on Mars s surface now. Mars has two very small moons. They are called Phobos and Deimos. Many space probes have been sent to Mars. 10. Circle the letter of each sentence that is true about Mars. a. Mars is called the red planet. b. There are two moons that orbit Mars. c. The surface of Mars is covered with water. 11. Is the following sentence true or false? No space probe has been sent to Mars. 12. What do scientists think formed the features on the surface of Mars? Circle the letter of the correct answer. a. the sun b. space probes c. water 341