The Outer Planets (pages 720 727) Gas Giants and Pluto (page 721) Key Concept: The first four outer planets Jupiter, Saturn, Uranus, and Neptune are much larger and more massive than Earth, and they do not have solid surfaces. The outer planets include Jupiter, Saturn, Uranus, Neptune, and Pluto. The first four outer planets Jupiter, Saturn, Uranus, and Neptune are called the gas giants. They are very large, and they do not have solid surfaces. The gas giants are made up mainly of hydrogen and helium. All the gas giants have many moons. Each gas giant is also surrounded by rings. A ring is a thin circle of small ice and rock particles around a planet. 1. Circle the letter of the sentence that is true about gas giants. a. They have rocky surfaces. b. They have no moons. c. They do not have solid surfaces. 2. Each of the gas giants is surrounded by circles called. 342
3. Complete the concept map about the outer planets. Outer planets include Gas giants Pluto include a. b. Uranus Saturn Jupiter (pages 722 723) Key Concept: Jupiter is the largest and most massive planet. Jupiter s mass is about 2 1 / 2 times the mass of all the other planets combined. Jupiter has a thick atmosphere made up mainly of hydrogen and helium. A storm in Jupiter s atmosphere is called the Great Red Spot. Jupiter has more than 60 moons. The four largest moons are Io (EYE oh), Europa, Ganymede, and Callisto. 343
ideas on page 343. 4. Circle the letter of each sentence that is true about Jupiter. a. Jupiter is the largest planet. b. Jupiter has a thick atmosphere. c. Jupiter has no moons. 5. Is the following sentence true or false? The Great Red Spot is a storm in Jupiter s atmosphere. 6. Circle the letter of a moon of Jupiter. a. Europa b. Saturn c. Great Red Spot Saturn (page 724) Key Concept: Saturn has the most spectacular rings of any planet. Saturn is the second-largest planet. Saturn s atmosphere is made up mostly of hydrogen and helium. Saturn has many rings. Saturn s rings are broad and thin. Saturn has more than 31 moons. Saturn s largest moon is named Titan. Titan is larger than the planet Mercury. 7. Is the following sentence true or false? Saturn is the second-largest planet. 344
8. The picture shows the sun and the planets of the solar system. Draw a circle around the planet Saturn. Sun Earth Mercury Venus Mars 9. Circle the letter of each sentence that is true about Saturn. a. Saturn s rings are broad and thin. b. Saturn s largest moon is named Titan. c. Saturn s atmosphere is made up mostly of hydrogen and helium. Uranus (page 725) Key Concept: Uranus s axis of rotation is tilted at an angle of about 90 degrees from the vertical. Uranus looks blue-green from Earth because there is methane gas in its atmosphere. Uranus is surrounded by a group of thin, flat rings. Uranus s axis is different than the axes of other planets. Uranus looks like it is rotating from top to bottom. Other planets look like they are rotating from side to side. Uranus has over 25 moons. Uranus s five largest moons have icy surfaces with many craters. 345
ideas on page 345. 10. Circle the letter of each sentence that is true about Uranus. a. Uranus has no rings. b. Uranus has no moons. c. Uranus looks blue-green from Earth. 11. Is the following sentence true or false? Uranus looks like it is rotating from top to bottom. Neptune (page 726) Key Concept: Neptune is a cold, blue planet. Its atmosphere contains visible clouds. Neptune is much like Uranus in size and color. Neptune looks blue from Earth. Neptune s atmosphere has clouds. Scientists think that Neptune is shrinking. Neptune has at least 13 moons. Neptune s largest moon is called Triton. 12. Is the following sentence true or false? There are no clouds in Uranus s atmosphere. 13. Circle the letter of each sentence that is true about Neptune. a. Neptune s largest moon is called Triton. b. Scientists think that Neptune is shrinking. c. Neptune is much larger than Uranus. 346
Pluto (page 727) Key Concept: Pluto has a solid surface and is much smaller and denser than the other outer planets. Pluto is the farthest planet from the sun. Pluto is very different than the gas giants. For example, Pluto has a solid surface. Pluto is smaller than Earth s moon. Pluto is so small that some astronomers do not think it should be called a planet. 14. Is the following sentence true or false? Pluto is the nearest planet to the sun. 15. Pluto is smaller than Earth s. 347