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Table of Contents The Solar System Section 1 • Planet Motion Section 2: The Inner Planets Section 3: The Outer Planets Section 4: Life in the Solar System Section 1 Planet Motion Models of the Solar System • In the geocentric model of the solar system, Earth is considered the center and everything else revolves around it. • This model was developed by the Greek philosopher Ptolemy. Section 1 Planet Motion Heliocentric Model • Earth-centered model held until 1543 when Polish astronomer Nicholas Copernicus proposed a different view. • Copernicus stated that the Moon revolves around Earth. • Earth and the other planets revolve around the Sun. Section 1 Planet Motion Heliocentric Model • The apparent motion of the planets, the stars, and the Sun is due to Earth’s rotation. This is the heliocentric model, or Sun-centered model of the solar system. Section Planet Motion 1 Galileo • Using his telescope, Italian astronomer Galileo Galilei discovered evidence to support Copernicus’s model. • He observed that Venus went through phases like the Moon’s. • He also saw moons in orbit around Jupiter. Section 1 Planet Motion Understanding the Solar System • In the early 1600’s, the German astronomer Johannes Kepler discovered the planets travel around the Sun in ellipses, not perfect spheres. • Planets travel at different speeds in their orbits. • The closer a planet is to the Sun, the faster it completes its orbit. • The astronomical unit (AU) equals the average distance from Earth to the Sun, about 150 million km. Section 1 Planet Motion Classifying the Planets • One system uses size, structure, and composition. • Those similar to Earth are called terrestrial planets. Giant planets are jovian planets. • Two other systems classify planets by location. Section 1 Planet Motion Classifying the Planets • Planets whose orbits are between the Sun and the asteroid belt are classified as inner planets and those beyond the asteroid belt are outer planets. • Another system classifies planets whose orbits are between Earth’s orbit and the Sun as inferior planets, and those whose orbits are beyond Earth’s orbit as superior planets. Section 1 Planet Motion Other Solar Systems • Extrasolar planets—planets in orbit around other stars—are helping astronomers learn how planetary systems form. • As of 2009, astronomers have discovered more than 300 extrasolar planets in the universe. Section 1 Section Check Question 1 Who was responsible for developing the geocentric model of the solar system? A. Aristotle B. Copernicus C. Galileo D. Ptolemy Section 1 Section Check Answer The answer is D. Ptolemy presented his geocentric model of the solar system in 140 A.D. Section Section Check 1 Question 2 What is the length of an astronomical unit? A. 100 km B. 100 million km C. 150 million km D. 200 billion km Section 1 Section Check Answer The answer is C. One astronomical unit equals the average distance from Earth to the Sun, about 150 million km. Section 1 Section Check Question 3 _______ are planets in orbit around stars other than our Sun. A. Extrasolar planets B. Extrasensory planets C. Intersolar planets D. Intrasolar planets Section 1 Section Check Answer The answer is A. Scientists have discovered extrasolar planets around Upsilon Andromedae. Section 2 The Inner Planets Planets Near the Sun • The smallest and closest planet to the Sun is Mercury. • Mercury is covered by craters. • Mercury has a much larger iron core than would be expected and is missing some lighter materials. Section 2 The Inner Planets Planets near the Sun • Mercury has a large iron core and thin outer layers. • Mercury’s surface is covered with craters and cliffs up to 3km high. • Mercury has no true atmosphere. • Surface temperatures vary from 430ºC to -170ºC. Section The Inner Planets 2 Venus • Venus is the second planet from the Sun. • Venus is often referred to as Earth’s sister planet because their sizes and masses are almost identical. • Venus is blanketed by a dense atmosphere. Section 2 The Inner Planets The Greenhouse Effect • The clouds on Venus are so dense that only two percent of sunlight reaches the surface. • Heat radiated from Venus’s surface is absorbed by the carbon dioxide gas, causing what is called a greenhouse effect. • Due to this intense greenhouse effect, temperatures on the surface of Venus are between 450ºC and 475ºC. Section The Inner Planets 2 Earth • The third planet from the Sun is Earth. • Temperatures on Earth allow water to exist as a solid, a liquid, and a gas. • Ozone in Earth’s atmosphere protects life from the Sun’s intense radiation. Section 2 The Inner Planets Life on Earth • Life has been discovered in extreme environments on Earth. • These environments include vents on the seafloor, acidic hot springs, and ice in dark, cold polar waters Section The Inner Planets 2 Mars • The fourth planet from the Sun, Mars, is called the red planet because of iron oxide in some of the weathered rocks. • Other Martian features are the polar ice caps, composed of frozen carbon dioxide and frozen water. • Changes in the coloration and size of ice caps have been observed. • Coloration changes are seasonal due to wind blowing lighter colored dust off the darker colored dust below. Section The Inner Planets 2 Mars • The Martian atmosphere is much thinner than Earth’s and is composed mostly of carbon dioxide, some nitrogen and, argon. • Mars has two small, heavily cratered moons called Phobos and Deimos. Section 2 The Inner Planets Was Mars Once Wet? • In late 2003, NASA sent martian landers Spirit and Opportunity in search of liquid water. • NASA’s Mars Reconnaissance Orbiter discovered sediment layering and gullies in 2009. Section 2 The Inner Planets NASA on Mars • The Mariner 9 space probe orbited Mars in 1971-1972. • Valles Marineris is a large canyon that was discovered by this early mission. • Mariner 9 also found large, extinct volcanoes on Mars. Section 2 The Inner Planets The Viking Probes • In 1976, the Viking 1 and Viking 2 probes landed on Mars. • The Viking 1 and Viking 2 orbiters photographed the entire surface of Mars from orbit. • Landers conducted meteorological, chemical, and biological experiments on the planet’s surface. Section 2 The Inner Planets Global Surveyor, Pathfinder, and Odyssey • In 1996, Global Surveyor showed that the walls of Valles Marineris have distinct layers similar to those of the Grand Canyon in Arizona. • Mars Odyssey, provided evidence for water as frost beneath a thin layer of soil in the far northern and southern parts of Mars. • The Mars Pathfinder and its rover, Sojourner, gathered data that indicated that iron in Mar’s crust may have been leached out by groundwater. Section 2 Section Check Question 1 Which planet is closest to the Sun? A. Mars B. Mercury C. Earth D. Venus Section 2 Section Check Answer The answer is B. Mercury is the closest planet to the Sun. Venus is the second planet from the Sun. Section Section Check 2 Question 2 Which planet has a size and a mass similar to Earth’s? A. Jupiter B. Mercury C. Pluto D. Venus Section 2 Section Check Answer The answer is D. Venus has similar size and mass but the temperatures on its surface are between 450º C and 475º C. Section 2 Section Check Question 3 Earth is the __________ planet from the Sun. A. second B. third C. fourth D. fifth Section 2 Section Check Answer The answer is B. Mercury and Venus are closer to the Sun than Earth. Section The Outer Planets 3 Jupiter • The largest and fifth planet from the Sun is Jupiter. • It is composed mostly of hydrogen and helium. • Continuous storms of swirling, high-pressure gas have been observed on Jupiter. • The Great Red Spot is the most spectacular of these storms. Section 3 The Outer Planets The Voyager Probes and Galileo • In 1979, Voyager1 and Voyager 2 flew past Jupiter, and the Galileo space probe reached Jupiter in 1995. • The major discoveries of these probes include information about the composition and motion of Jupiter’s atmosphere, characteristics of some of its moons and the discovery of new moons and faint rings. Section 3 The Outer Planets Jupiter’s Moons • Jupiter has 63 known moons. Many are small, rocky bodies that could be captured asteroids. • Four are large enough to be considered small planets. • These Galilean moons of Jupiter are Io, Europa, Ganymede, and Callisto. • NASA scientists believe liquid water exists beneath Europa, Ganymede, and Callisto’s surfaces. Section 3 The Outer Planets Jupiter’s Moons • Ganymede is larger than the planet Mercury and is the largest moon in the solar system. • Io is under a constant tug-of-war between the gravities of Jupiter and Europa. • This heats up the interior of Io and causes it to be the most volcanically active body in the solar system. • Europa is ice-covered. Section The Outer Planets 3 Saturn • Saturn is the sixth planet from the Sun and has the largest and most complex ring system of any outer planet. • Saturn is a large planet with a thick outer atmosphere composed of hydrogen mostly and helium with some ammonia, methane, and water vapor. Section 3 The Outer Planets Saturn’s Rings • Saturn’s rings are composed of billions of ice and rock particles ranging in size from a speck of dust to tens of meters across. • The ring system is over 280,000 km wide and only 1 km thick. Section 3 The Outer Planets Cassini-Huygens • The Cassini-Huygens spacecraft approached Saturn in 2004 to collect data about Saturn, its ring system and many moons. • In January 2005, Huygens passed by Saturn’s largest moon Titan in search of hydrocarbons. Section The Outer Planets 3 Uranus • Uranus is the seventh planet from the Sun. • It is four times larger than Earth with 27 moons. • The atmosphere of Uranus contains hydrogen, helium, and about two percent methane. • The methane gives the planet its blue-green color. • Uranus’s axis of rotation is tilted, so that it is nearly parallel to the plane of its orbit. Section The Outer Planets 3 Neptune • Neptune is the eighth planet from the Sun. • Neptune’s atmosphere is similar to that of Uranus, but has a little more methane—about 3 percent—causing it to look bluer. • Voyager 2 passed by Uranus in 1986 and Neptune in 1989, the only spacecraft to fly-by each planet. Section 3 The Outer Planets Dwarf Planets • In 2005, astronomers discovered Eris, an object beyond Pluto, that is larger than Pluto. • This discovery led to a change in the definition of a planet. • Pluto, Eris and a large asteroid named Ceres are now classified as dwarf planets. • Dwarf planets are nearly round objects in orbit around the Sun that are not satellites and have not cleared the debris in their orbits. Section 3 The Outer Planets Comets and Other Objects • A comet, is composed of dust and rock particles mixed with frozen water, methane, and ammonia. • As a comet approaches the Sun, it begins to vaporize. The vaporized dust and gases form a bright cloud called a coma around the nucleus. The solar wind pushes on the vaporized coma, forming a tail that always points away from the Sun. Section 3 The Outer Planets Comets and Other Objects • Most comets come from two places—a vast disk of icy comets called the Kuiper Belt near Neptune’s orbit and the Oort cloud. • Once in orbit around the Sun, comets reappear at predictable times. Section The Outer Planets 3 Asteroids • Rocky objects formed from material similar to that of the planets are called asteroids. • Most asteroids are found in a belt between the orbits of Mars and Jupiter. • Asteroids range in size from tiny particles to objects 500 km in diameter. Section The Outer Planets 3 Meteoroids • Sand-to-boulder sized objects within the solar system are called meteoroids. • Meteoroids may enter the atmosphere. • Most burn up completely and we see them as meteors or “shooting stars.” • Others do not burn completely and strike Earth. • These are called meteorites. Section The Outer Planets 3 Sedna • Sedna has been labeled a distant planetoid and with a diameter of 1,200 to 1,700 km, it is smaller than Pluto, but larger than comets in the Kuiper Belt. Artist rendition Section 3 Section Check Question 1 The fifth planet from the Sun is __________. A. Jupiter B. Neptune C. Saturn D. Pluto Section 3 Section Check Answer The answer is A. Jupiter is also the largest planet in the solar system. Section 3 Section Check Question 2 Which of Jupiter’s four largest moons most volcanically active object in the solar system? A. Callisto B. Europa C. Ganymede D. Io Section 3 Section Check Answer The answer is D. Jupiter exerts tremendous gravitational pull on Io. Section 3 Section Check Question 3 Which one of the following is NOT classified as a dwarf planet? A. Pluto B. Eris C. Ganymede D. Ceres Section 3 Section Check Answer The answer is C. Ganymede is one of Jupiter’s four largest moons. Section 4 Life in the Solar System Life as We Know It • A research submarine, named Alvin, found some interesting life-forms while exploring hot, volcanic vents on the ocean floor. • Life-forms found included crabs, clams, and tubeworms. • Alvin also discovered colonies of bacteria living off the superheated, chemically enriched fluids erupting from volcanic vents. Section 4 Life in the Solar System Can life exist on other worlds? • Extraterrestrial life is life beyond Earth. • Let’s take a look at some places where scientists are searching for extraterrestrial life. Section Life in the Solar System 4 Mars • Evidence from recent missions to Mars has shown that the planet probably had large amounts of water on its surface in the past. • If life existed and left evidence, future landers or astronauts will find it. Section 4 Life in the Solar System Europa • Europa’s ocean could hold more than twice the amount of water that Earth’s oceans hold. • If life can exist in extremely hot liquid flowing from volcanic vents on Earth’s ocean floor, could it not exist in a similar environment if it exists on Europa? Section Life in the Solar System 4 Titan • Saturn’s moon, Titan, is larger than Mercury and has an atmosphere composed mostly of nitrogen, with some argon and methane. • The presence of hydrocarbons on the surface of Titan interests exobiologists, scientists who search for evidence of life on other worlds. Section Life in the Solar System 4 Titan • The apparent absence of large impact craters indicates that Titan has experienced internal geologic activity. • This activity could provide the energy needed for organic molecules to develop into the building blocks of life. Section 4 Section Check Question 1 What is extraterrestrial life? Answer Extraterrestrial life is life that exists beyond Earth. Section 4 Section Check Question 2 What makes scientists think that Europa’s subsurface ocean could contain life? Answer Scientists think that the ocean might be deep and longlasting, possibly even liquid water that is warmed by Jupiter’s gravitational pull on Europa. Section 4 Section Check Question 3 Which performed tests for water on Mars? A. Alvin B. Huygens probe C. Galileo probe D. Spirit and Opportunity Section 4 Section Check Answer The answer is D. Spirit and Opportunity discovered evidence of hematite, which forms in the presence of water. Help To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow. Click on this icon to return to the table of contents. Click on this icon to return to the previous slide. Click on this icon to move to the next slide. Click on this icon to open the resources file. Click on this icon to go to the end of the presentation. End of Chapter Summary File Chapter Resources Click on one of the following icons to go to that resource. connected.mcgraw-hill.com/ Image Bank Chapter Summary Chapter Review Questions Standardized Test Practice Image Bank Click on individual thumbnail images to view larger versions. Image Bank Geocentric Model THUMBNAILS Image Bank Heliocentric Model THUMBNAILS Image Bank Our Solar System THUMBNAILS Image Bank Sedna (artist rendition) THUMBNAILS Reviewing Main Ideas Planet Motion • In the geocentric model of the solar system, Earth is in the center. In the heliocentric model, the Sun is in the center. • The position of a planet in orbit around the Sun can be shown by heliocentric longitude. Reviewing Main Ideas Planet Motion • Inner planets have orbits closer to the Sun than the asteroid belt; outer planets have orbits beyond the asteroid belt. • A large nebula fragmented into smaller ones, one of which later condensed and flattened to form the solar system. Reviewing Main Ideas The Inner Planets • Mercury has a larger iron core than expected for a planet its size. • The carbon dioxide in Venus’s dense atmosphere has caused an extreme greenhouse effect that produces very high surface temperatures. • Mars landers have provided evidence that Mars once had more water on its surface than it does today. Reviewing Main Ideas The Outer Planets • Jupiter is the largest planet in the solar system and has many moons. Four of these moons were first seen by Galileo. • Saturn has the most complex ring system of all outer planets and is the second largest planet. Reviewing Main Ideas The Outer Planets • The green-blue color of Uranus and the blue color of Neptune are caused by methane in their atmosphere. • Pluto, Eris and Ceres are dwarf planets. • Comets, asteroids, and meteoroids also orbit the Sun. Reviewing Main Ideas Life in the Solar System • Life exists in extreme environments on Earth and may be able to survive in extreme environments on other planets. • Europa is considered the most promising location in the solar system to look for extraterrestrial life. • Mars and Titan might have harbored life sometime in the past. Chapter Review Question 1 What view of the solar system was prevalent among early Greek scientists? Answer Many early Greeks thought that the Sun and Moon rotated around Earth, and that the stars were in a separate sphere that also rotated around Earth. Chapter Review Question 2 Which of these planets has a very thin atmosphere? A. Earth B. Mars C. Mercury D. Venus Chapter Review Answer The answer is C. Mercury has a low gravitational pull and most gases that could form an atmosphere escape into space. Chapter Review Question 3 The most well-studied planet in our solar system other than Earth is _____. A. Mars B. Mercury C. Saturn D. Venus Chapter Review Answer The answer is A. Missions to Mars have long been a focus of NASA. Chapter Review Question 4 What is the Great Red Spot of Jupiter? Answer The Great Red Spot of Jupiter is a continuous storm of high-pressure gas. Chapter Review Question 5 __________ gives Neptune a bluish-green color. A. Ammonia B. Methane C. Nitrogen D. Oxygen Chapter Review Answer The answer is B. Neptune’s atmosphere is similar to that of Uranus. Its methane content gives it a bluish-green color. Standardized Test Practice Question 1 Which two adjacent planets have the greatest distance between them? Standardized Test Practice Question 1 A. Jupiter and Saturn B. Mars and Jupiter C. Uranus and Neptune D. Venus and Earth Standardized Test Practice Answer The answer is C. Uranus and Neptune are nearly 11 AUs apart. Standardized Test Practice Question 2 Which planet has an orbital speed closest to that of Earth? A. Jupiter B. Mars C. Mercury D. Venus Standardized Test Practice Answer The answer is D. The orbital speed of Venus and Earth differ by 5 km/s. Standardized Test Practice Question 3 The area between Mars and Jupiter that contains the particles shown in the diagram is the __________. A. asteroid belt B. comet belt C. meteor shower D. Oort cloud Standardized Test Practice Answer The answer is A. Most asteroids are located in the asteroid belt between the orbits of Mars and Jupiter. Standardized Test Practice Question 4 This diagram illustrates that as Mercury’s core began to solidify, __________ resulted from breaks in the crust. A. cliffs B. craters C. maria D. storms Standardized Test Practice Answer The answer is A. The cliffs on the surface provide evidence that Mercury shrank. Standardized Test Practice Question 5 On which Sol was the low temperature the warmest? A. 1 B. 3 C. 4 D. 5 Standardized Test Practice Answer The answer is D. After the fifth Sol, the low temperature was about 10º C warmer than on the other four days. Help To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow. Click on this icon to return to the table of contents. Click on this icon to return to the previous slide. Click on this icon to move to the next slide. Click on this icon to open the resources file. Click on this icon to go to the end of the presentation. End of Chapter Resources File