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Chapter 21 A Family of Planets Table of Contents Section 1The Nine Planets Section 2The Inner Planets Section 3The Outer Planets Section 4Moons Section 5Small Bodies in the Solar System
Chapter 21 Section 1The Nine Planets Bellringer Create a mnemonic device to help you remember the order of the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto Example: My very eccentric mother just sent us nine pigs.
Chapter 21 Section 1The Nine Planets Objectives • List the planets in the order in which they orbit the sun. • Explain how scientists measure distances in space. • Describe how the planets in our solar system were discovered. • Describe three ways in which the inner planets and outer planets differ.
Chapter 21 Section 1The Nine Planets Our Solar System Our solar system includes the sun, the planets, and many smaller objects.
Chapter 21 Section 1The Nine Planets The Inner and Outer Solar Systems • The Inner Planets The planets closest to the sun include Mercury, Venus, Earth, and Mars. • Terrestrial planets • The Outer Planets The outer planets include Jupiter, Saturn, Uranus, Neptune, and Pluto. • Gas Giants
Chapter 21 Section 1The Nine Planets The Discovery of the Solar System • Early Knowledge Up until the 17th century, the universe was thought to only contain Earth, Venus, Mercury, Venus, Mars, Jupiter, Saturn, the sun, and Earth’s moon. • Using a Telescope After the invention of the telescope by the end of the 17th century, the moons of Jupiter and Saturn were discovered. • By the end of the 18th century, Uranus & 2 of its moons • By the end of the 19th century, Neptune and moons of other planets • Modern Times By the 20th century, Pluto and many other bodies had been discovered.
Chapter 21 Section 1The Nine Planets Measuring and Interplanetary Distances Scientists use the astronomical unit to measure distances in space. One astronomical unit is the average distance between the sun and Earth, or approximately 150,000,000 km.
Chapter 21 Section 1The Nine Planets
Chapter 21 Section 2The Inner Planets Objectives • Explain the difference between a planet’s period of rotation and period of revolution. • Describe the difference between prograde and retrograde rotation. • Describe the individual characteristics of Mercury, Venus, Earth, and Mars. • Identify the characteristics that make Earth suitable for life.
Chapter 21 Section 2The Inner Planets Mercury: Closest to the Sun Mercury is a very hot, small planet. It only takes Mercury 88 days to revolve around the sun.
Chapter 21 Section 2The Inner Planets Venus: Earth’s Twin? • The Atmosphere of Venus Of all the inner planets, Venus has the densest atmosphere. • Mapping Venus’s Surface The Magellan spacecraft mapped the surface of Venus by using radar waves.
Chapter 21 Section 2The Inner Planets Earth: An Oasis in Space • Water on Earth Earth is warm enough to keep most of its water from freezing and cool enough to keep its water from boiling away. Liquid water is important to life on Earth. • The Earth from SpaceSatellites are used tostudy the Earth fromspace in order to betterunderstand global systems.
Chapter 21 Section 2The Inner Planets Mars: Our Intriguing Neighbor • The Atmosphere of Mars Mars has a thin atmosphere with low air pressure. • Water on Mars Liquid water cannot exist on Mars’s surface today, but most likely it was there in the past.
Chapter 21 Section 2The Inner Planets Mars: Our Intriguing Neighbor, continued • Where Is the Water Now? Mars has two polar icecaps made of frozen water and carbon dioxide. Many scientists think that there is more frozen water beneath the Martian soil • Martian Volcanoes Mars has two large volcanic systems, one of which includes the largest mountain in the solar system.
Chapter 21 Section 2The Inner Planets Mars: Our Intriguing Neighbor, continued • Missions to Mars Several recent missions to Mars were launched to gain a better understanding of the planet.
Chapter 21 Section 3The Outer Planets Bellringer All planets with atmospheres have weather. Jupiter’s Great Red Spot appears to be very similar to a hurricane system on Earth, but it has lasted for centuries, driven by the planet’s internal thermal energy. Write or tape-record a humorous but accurate weather forecast for one of the planets with an atmosphere.
Chapter 21 Section 3The Outer Planets Objectives • Explain how gas giants are different from terrestrial planets. • Describe the individual characteristics of Jupiter, Saturn, Uranus, Neptune, and Pluto.
Chapter 21 Section 3The Outer Planets Jupiter: A Giant Among Giants • Jumbo Sized Jupiter is the largest planet in our solar system. • NASA Missions to Jupiter NASA has sent five missions to Jupiter to study Jupiter’s atmosphere and moons.
Chapter 21 Section 3The Outer Planets Saturn: Still Forming • The Rings of Jupiter Saturn’s rings are the largest of all of the gas giants’ rings. • NASA Exploration of Saturn Launched in 1997, the Cassini spacecraft is designed to study Saturn’s rings, moon, and atmosphere.
Chapter 21 Section 3The Outer Planets Uranus: A Small Giant • Uranus’s Atmosphere The atmosphere of Uranus is mainly hydrogen and methane, which makes the planet appear to be blue-green in color.
Chapter 21 Section 3The Outer Planets Uranus: A Small Giant, continued • A Tilted Planet Unlike most other planets, Uranus is tipped over on its axis. So its axis of rotation is tilted by almost 90° and lies almost in the plane of its orbit.
Chapter 21 Section 3The Outer Planets Neptune: The Blue World • Discovery of Neptune Neptune was not discovered until 1846. • The Atmosphere of Neptune The composition of Neptune’s atmosphere is similar to that of Uranus’s atmosphere, but Neptune has belts of clouds that are much more visible.
Chapter 21 Section 3The Outer Planets Pluto: The Mystery Planet • A Small World Less than half the size of Mercury, Pluto is the smallest planet in the solar system. • A True Planet? BecausePluto is so small andunusual, some scientiststhink that is should notbe classified as a planet.Some scientists classifyPluto as a large asteroidor comet.
Chapter 21 Section 4Moons Bellringer The first astronauts to land on the moon were quarantined after their mission. NASA wanted to make sure that the astronauts didn’t bring back any disease-causing organisms from the moon. Discuss whether or not they think this would be possible.
Chapter 21 Section 4Moons Objectives • Describe the current theory of the origin of Earth’s moon. • Explain what causes the phases of Earth’s moon. • Describe the difference between a solar eclipse and a lunar eclipse. • Describe the individual characteristics of the moons and other planets.
Chapter 21 Section 4Moons Luna: The Moon of Earth • The Surface of the Moon The surfaces of bodies that have no atmospheres, such as the moon, preserve a record of almost all of the impacts that the bodies have had.
Chapter 21 Section 4Moons Luna: The Moon of Earth, continued • Lunar Origins The next slide shows how scientists think the moon probably formed. • Current Theory : The moon formed from a piece of Earth’s mantle which broke off during a collision between Earth and a large object • Supported by the fact that the moon has a composition similar to the Earth’s mantle
Chapter 21 Section 4Moons
Chapter 21 Section 4Moons Luna: The Moon of Earth, continued • Phases of the Moon The different appearances of the moon due to its changing position are called phases. The moon takes 29.5 days to get through all of it’s phases. • Waxing and Waning When the moon is waxing, the sunlit fraction that we can see from Earth is getting larger. When the moon is waning, the sunlit fraction is getting smaller.
Chapter 21 Section 4Moons
Chapter 21 Section 4Moons Solar Eclipse • Occurs when the new moon comes between the Earth and the sun • Shadow of moon falls on part of the Earth
Chapter 21 Section 4Moons Luna: The Moon of Earth, continued • Eclipses When the shadow of one celestial body falls on another, an eclipse occurs. • Solar Eclipses During a total solar eclipse, the disk of the moon completely covers the disk of the sun, as shown below.
Chapter 21 Section 4Moons Lunar Eclipse • Occurs when the Earth comes between the sun and moon • Shadow of Earth falls on the moon • The moon is red because when sunlight passes through Earth’s atmosphere, blue light is filtered out
Chapter 21 Section 4Moons Luna: The Moon of Earth, continued • Lunar Eclipses During a lunar eclipse, the moon passes through the Earth’s shadow. • The Tilted Orbit of the Moon You don’t see a solar and lunar eclipse every month because the moon’s orbit around the Earth is tilted.
Chapter 21 Section 4Moons The Moons of Other Planets • The Moons of Mars Mars’s two moons, Phobos and Deimos, are small, oddly shaped satellites. • Large & rocky, asteroids caught by Mars’s gravity • The Moons of Jupiter Jupiter has dozens of moons. Liquid water may be beneath the surface of the moon Europa. • Largest 4 : Ganymede, Callisto, Io, and Europa • Known as Galilean satellites • Io is the closest and the most volcanically active • Europa may have liquid water
Chapter 21 Section 4Moons The Moons of Other Planets, continued • The Moons of Saturn Like Jupiter, Saturn has dozens of moons. Most of these moons are small bodies of mostly frozen water but some contain rocky material. • Largest : Titan, believe that Earth may have looked this way before life evolved • The Moons of Uranus Uranus has several moons. Uranus’s largest moons are made of ice and rock and are heavily cratered. • Most unusual: Miranda
Chapter 21 Section 4Moons The Moons of Other Planets, continued • The Moons of Neptune • Several moons which are small and rocky. • Largest is Triton • Triton has a retrograde orbit and a thin nitrogen atmosphere • Triton’s surface is frozen nitrogen and methane, volcanoes eject nitrogen into the air
Chapter 21 Section 5Small Bodies in the Solar System Bellringer Have scientists ever brought extraterrestrial material to Earth? Scientists have studied rocks from Mars and other parts of the solar system. How did scientists obtain these rocks? Record your response in your science journal.
Chapter 21 Section 5Small Bodies in the Solar System Objectives • Explain why comets, asteroids, and meteoroids are important to the study of the formation of the solar system. • Describe the similarities of and differences between asteroids and meteoroids. • Explain how cosmic impacts may affect life on Earth.
Chapter 21 Section 5Small Bodies in the Solar System Comets • What Is a Comet? A small body of ice, rock, and cosmic dust loosely packed together is called a comet. • Formed in the cold, outer solar system back when the planets were formed, thus each is a sample of the early solar system • Has a solid center called a nucleus • No tail until it nears the sun
Chapter 21 Section 5Small Bodies in the Solar System Comets • Comet Tails When a comet passes close enough to the sun, solar radiation heats the ice so that the comet gives off gas and dust in the form of a long tail. • Sometimes there are 2 tails – one made of dust, and one made of ions, which are made of electrically charged particles, the ion tail points away from the sun when blown by solar wind
Chapter 21 Section 5Small Bodies in the Solar System Comets, continued • Comet Orbits The orbits of all bodies that move around the sun are ellipses. A comet’s ion tail always points away from the sun. • Comet Origins Many scientists think that comets come from the Oort Cloud, a spherical region that surrounds the solar system, or from the Kuiper Belt
Chapter 21 Section 5Small Bodies in the Solar System Asteroids • What Are Asteroids? Small, rocky bodies that revolve around the sun are called asteroids. • Types of Asteroids Asteroids mostly have irregular shapes, larger ones are spherical • Located in the asteroid belt, between Mars and Jupiter
Chapter 21 Section 5Small Bodies in the Solar System Meteoroids • What Are Meteoroids? A meteoroid is a small, rocky body that revolves around the sun. • Similar, but smaller than asteroids • Most burn up in the atmosphere, giving off light and heat energy • .
Chapter 21 Section 5Small Bodies in the Solar System Meteorites • Meteor Showers You can see a large number of meteors during a meteor shower as Earth passes through the dusty debris of comets. • Types of Meteorites Meteorites have different compositions. The three major types of meteorites are stony, metallic, and stony-iron meteorites. • Stony - contain organic materials and water • Metallic - made of iron and nickel • Stony-iron – made of iron and nickel
Chapter 21 Section 5Small Bodies in the Solar System The Role of Impacts in the Solar System • Future Impacts on Earth? Scientists estimate that impacts that are powerful enough to cause a natural disaster might happen once every few thousand years. • Often result in craters • Planets with no atmosphere have more impacts • Large impacts occur every few hundred years
Chapter 21 Section 5Small Bodies in the Solar System The Role of Impacts in the Solar System • The Torino Scale The Torino scale is a system that allows scientists to rate the hazard level of an object moving toward Earth. • 0 = small chance of striking Earth • 5,6,7 = highly likely to hit Earth • 8,9,10 = collision is certain (capable of causing a global catastophe
Chapter 21 A Family of Planets Concept Map Use the terms below to complete the concept map on the next slide.