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Transcript
The Solar System Section 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. The Solar System The Inner Planets Section 2 The Solar System Section 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. The Solar System Section 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. The Solar System Section 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. The Solar System Section 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. The Solar System Section 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 The Solar System Section 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. The Solar System The Gas Giants Section 2 The Solar System Section 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. The Solar System Section 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. The Solar System Section 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. The Solar System Section 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. The Solar System Section 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.