1. The Solar SystemSection 2 The Inner Planets 〉 How are the inner planets similar to one another? 〉 The terrestrial planets are relatively small and have solid, rocky surfaces. terrestrial planet: one of the highly dense planets nearest to the sun: Mercury, Venus, Earth, and Mars.

2. The Solar SystemSection 2 The Inner Planets

3. The Solar SystemSection 2 The Inner Planets, continued Mercury has extreme temperatures. –Mercury is the closest planet to the sun. –One year there is only 88 days on Earth. –The side of Mercury facing the sun can reach 720 K. The side facing away from the sun is only 103 K. –Mercury is covered by craters.

4. The Solar SystemSection 2 The Inner Planets, continued Thick clouds on Venus cause a greenhouse effect. –Venus has a thick atmosphere containing large amounts of sulfuric acid. –The atmospheric pressure on Venus is 90 times that of Earth. –A runaway greenhouse effect keeps the surface temperature above 700 K.

5. The Solar SystemSection 2 The Inner Planets, continued Earth has ideal conditions for living creatures. –Earth is the only planet known to harbor life. hydrosphere: the portion of Earth that is water The atmosphere protects Earth from radiation. –Earth’s atmosphere is 78% nitrogen, 21% oxygen, and 1% carbon dioxide and other gases. –The atmosphere protects Earth from harmful radiation and high-energy particles emitted by the sun.

6. The Solar SystemSection 2 The Inner Planets, continued Many missions have explored the planet Mars. Mars has many extreme landforms. –The Martian volcano Olympus Mons is the largest mountain in the solar system. –The surface of Mars is red from large amounts of iron oxide in the soil.

7. The Solar SystemSection 2 The Inner Planets, continued An asteroid belt lies beyond the orbit of Mars. –The dwarf planet Ceres is in the asteroid belt. asteroid: a small, rocky object that orbits the sun; most asteroids are located in a band between the orbits of Mars and Jupiter dwarf planet: a celestial body that orbits the sun, is round because of its own gravity, but has not cleared its orbital path

8. The Solar SystemSection 2 The Gas Giants 〉 What are gas giants? 〉 The outer planets are much larger than the inner planets and have thick, gaseous atmospheres, many satellites, and rings. A gas giant is a planet that has a deep, massive atmosphere: Jupiter, Saturn, Uranus, and Neptune. All the gas giants have rings and satellites.

9. The Solar SystemSection 2 The Gas Giants

10. The Solar SystemSection 2 The Gas Giants, continued Jupiter is the largest planet in the solar system. –Jupiter is big enough to hold 1300 Earths. –Jupiter rotates once around its axis in less than 10 hours. –Jupiter’s atmosphere has swirling clouds of hydrogen, helium, methane, and ammonia. –Jupiter has more than 60 satellites.

11. The Solar SystemSection 2 The Gas Giants, continued Saturn has the most extensive ring system. –Saturn is 95 times the mass of the Earth and takes over 29 y to orbit the sun. It rotates in 10.7 h. –Saturn’s rings are narrow bands of tiny particles of dust, rock, and ice. –Saturn has more than 40 satellites. –Saturn may still be forming. –Saturn radiates three times more energy than it receives from the sun.

12. The Solar SystemSection 2 The Gas Giants, continued Uranus and Neptune are blue gas giants. –They hold thick, gaseous atmospheres composed of hydrogen, helium, and methane. –The methane gives both planets a bluish color. –Uranus is 14 Earth masses, and it takes about 84 y to orbit the sun at its distance of 19 AU. –Neptune is 17 Earth masses, and takes approximately 164 y to orbit the sun at a distance of 30 AU.

13. The Solar SystemSection 2 Beyond the Gas Giants 〉 What type of bodies lie beyond the gas giants? 〉 Beyond the gas giants are numerous small bodies composed of ice and rock. Not all large objects in the solar system are planets. –The scientific definition of planet was decided upon in 2006 by the International Astronomical Union. –Pluto, formerly considered a planet, was reclassified as a dwarf planet.

14. The Solar SystemSection 2 Beyond the Gas Giants, continued There are many objects beyond Neptune. –Beyond Neptune lies the Kuiper Belt. –The Kuiper Belt contains many small bodies of ice and rock. –Scientists think that these bodies are the remnants of the material that formed the solar system. –At least two dwarf planets, Pluto and Eris, can be found in the Kuiper Belt.