Contents

Introduction 10

Chapter i: Asteroids 19

Major Milestones in Asteroid Research 20 Bode's Law 21

Later Advances in Asteroid Studies 22 Geography of the Asteroid Belt 22 Names and Orbits of Asteroids 23 Distribution and Kirkwood Gaps 23 Near-Earth Asteroids 25 Main-Belt Asteroid Families 27 Hungarias and Outer-Belt Asteroids 28 Trojan Asteroids 29 Asteroids in Unusual Orbits 30 The Difference Between Asteroids and Comets 30 Measuring Asteroids 31

Size and Albedo 31 Classification of Asteroids 33 Rotation and Shape 33 Mass and Density 35 Composition 36 Asteroid Taxonomic Classes 37 Spacecraft Exploration 38 Origin and Evolution of the Asteroids 41 Notable Asteroids 42 Ceres 42 Eros 44 Geographos 45 Hermes 45 Icarus 46 Pallas 46 Vesta 46

Chapter 2: Meteors and Meteorites 48

Basic Features of Meteors 49 Meteor Showers 51

Meteorites: Surviving Atmospheric Entry 53 Measurement of Meteoroid Orbits 57 Reservoirs of Meteoroids in Space 58 Directing Meteoroids to Earth 59

Meteorites 61 Recovery of Meteorites 62 Types of Meteorites 63 Chondrites 64 Achondrites 68 Iron Meteorites 70 Stony Iron Meteorites 71 Association of Meteorites with Asteroids 72 The Ages of Meteorites and Their Components 73

Cosmic-Ray Exposure Ages of Meteorites 76 Meteorites and the Formation of the Early Solar System 77 Meteorite Craters 80 The Impact-Cratering Process 82 Variations in Craters Across the Solar System 84 Meteorite Craters as Measures of Geologic Activity 85 Meteoritics 86 Notable Meteorites 87 Allende Meteorite 87 Ensisheim Meteorite 87 Murchison Meteorite 87 Orgueil Meteorite 88

Chapter 3: Jupiter 89

Basic Astronomical Data 90 Planetary Data for Jupiter 91 The Atmosphere 92 Nature of the Great Red Spot 93 Cloud Composition 94 Atmospheric Characteristics 95 Atmospheric Abundances for Jupiter 96

Temperature and Pressure 98

Other Likely Atmospheric

Constituents 99

Collision with a Comet and an

Asteroid 99

Radio Emission 101

The Magnetic Field and Magnetosphere 103 The Auroras 104 The Interior 104 Jupiter's Moons and Ring 107 The Galilean Satellites 107 Callisto 108 Ganymede 109 Europa 109 Io 110 Other Satellites 111 The Ring 112 Origin of the Jovian System 114 Early History of Jupiter 114 Early History of the Satellites 114

Chapter 4: Saturn 116

Basic Astronomical Data 117 Planetary Data for Saturn 118 The Atmosphere 119

The Magnetic Field and Magnetosphere 122 The Interior 123 Saturn's Rings and Moons 125 The Ring System 126 Moons 130

Their Orbits and Rotation 130 Titan 133 Mimas 137 Enceladus 138 Tethys 140 Dione 142 Rhea 143 Hyperion 144 Iapetus 144 Phoebe 146 Observations of Saturn from Earth 147 Spacecraft Exploration 147

Chapter 5: Uranus 149

Basic Astronomical Data 150 Planetary Data for Uranus 152 The Atmosphere 153

Planetary Magnetosphere

The Magnetic Field and Magnetosphere 155 The Interior 156 Uranus's Moons and Rings 157 Moons 157

Miranda 160 Ariel 161 Umbriel 162 Titania 162 Oberon 163 The Ring System 163 The Discovery of Uranus 164 Spacecraft Exploration 165

Chapter 6: Neptune 166

Planetary Data for Neptune 167 Basic Astronomical Data 168 The Atmosphere 168

The Magnetic Field and Magnetosphere 171 Interior Structure and Composition 172 Neptune's Moons and Rings 173 Moons 173 Triton 174

Proteus and Nereid 177 The Ring System 178 Neptune's Discovery 180 Later Observations from Earth 182 Spacecraft Exploration 183

Chapter 7: Pluto, the Kuiper Belt, and Beyond 184

Basic Data for Pluto 185 Basic Astronomical Data 186 The Atmosphere 186 The Surface and Interior 187 Pluto's Moons 189

Discovery of Pluto and Its Moons 190

The Kuiper Belt 192

Origin of Pluto and Its Moons 194

Pluto: Planet or Dwarf Planet? 195

The Oort Cloud 196

The Heliopause 197

Chapter 8: Comets 198

Basic Features 198 Designations 199 Early Observations 200

Halley and His Comet 200 Modern Cometary Research 203 Types of Orbits 204 Identifying Comets and Determining Their Orbits 205 Periodic Comets 206 Groups of Comets and Other Unusual

Cometary Objects 208 The Cometary Nucleus 209 The Gaseous Coma 212 Cometary Tails 215 Cometary Models 218 Origin and Evolution of Comets 219 Cometary Formation and the Oort Cloud 220 Possible Pre-Solar-System Origin of Comets 221 Notable Comets 222 Comet Arend-Roland 222 Biela's Comet 222 Chiron 222 Encke's Comet 223 Comet Hale-Bopp 223 Halley's Comet 223 Comet Hyakutake 225 Comet Ikeya-Seki 225 Comet Morehouse 226 Centaur Objects 226 Comet Schwassmann-Wachmann 227

Appendix A: Moons of Jupiter 228 Appendix B: Moons of Saturn 233 Appendix C: Moons of Uranus 238 Appendix D: Moons of Neptune 240 Appendix E: Notable Kuiper Belt Objects

Glossary 244

For Further Reading 246

Index 247

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