Planetary Science
The Science of Planets Around Stars
by George H.A. Cole and Michael M. Woolfson
Institute of Physics Publishing, 2002, 075030815X, Trade Paperback, VG condition, pen notes on front endpaper and small margin notes on a few pages, no spine creases, 508 pages.
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This book is concerned with structure of planets, the stars they orbit and the interactions between them. There are many planetary systems other than our own, but it is only through a detailed understanding of the relatively accessible bodies in our Solar System that a thorough appreciation of planetary science can be gained. This is particularly pertinent with the recent discovery of extra-solar planets and the desire to understand their formation and the prospect of life on other worlds.
Planetary science courses require an understanding of aspects from a wide range
of subjects, including astronomy, astrophysics, geophysics, geology and mineralogy. This text addresses the needs of these wide ranging interests and courses, as it assumes no prior knowledge of astrophysics or geophysics.
The book is written in two parts, making it suitable for students at different levels and approaching planetary science from differing backgrounds. Twelve independent descriptive chapters reveal our Solar System and the diverse bodies it contains; including satellites, planetary rings, asteroids, comets, meteorites and interstellar dust. These chapters are accompanied by 42 detailed topics that discuss specialised subjects in a quantitative manner and will be essential reading for those on higher level courses. These include mineralogy, stellar formation and evolution, Solar System dynamics, atmospheric physics, planetary interiors, thermodynamics, planetary astrophysics and exobiology. Problems and answers are also included.
In Planetary Science: The Science of Planets Around Stars Professors Cole and Woolfson present a complete overview of planetary science for students of physics, astronomy, astrophysics, earth sciences and geophysics. The novel approach taken makes the book suitable for students in various disciplines and from differing scientific backgrounds.
CONTENTS
CONTENTS
INTRODUCTION xix
A REVIEW OF THE SOLAR SYSTEM
1 THE UNITY OF THE UNIVERSE 1
1.1. Cosmic abundance of the chemical elements 1
1.2. Some examples 2
Problem 1 4
2 THE SUN AND OTHER STARS 6
2.1. The interstellar medium 6
2.2. Dense cool clouds 6
2.3. Stellar clusters 8
2.4. A scenario for formation of a galactic cluster 10
2.5. Main sequence stars and their evolution 12
2.6. Brown dwarfs 12
2.7. Stellar companions 12
Problem 2 15
3 THE PLANETS 16
3.1. An overview of the planets 16
3.2. Orbital motions 16
3.3. Orbits of the planets 19
3.4. Planetary structures general considerations 21
3.4.1. Planetary magnetic fields 24
Problems 3 26
4 THE TERRESTRIAL PLANETS 27
4.1. Mercury 27
4.1.1. The surface of Mercury 28
4.1.2. Mercury's magnetic field 31
4.1.3. Mercury summary 31
4.2. Venus 32
4.2.1. The surface of Venus 32
4.2.2. The atmosphere of Venus 35
4.2.3. Venus and magnetism 38
4.2.4. Venus summary 38
4.3 The Earth 38
4.3.1. The shape of the Earth 39
4.3.2. Surface composition and age 39
4.3.3. Changing surface features 41
4.3.4. Surface plate structure 41
4.3.5. Heat flow through the surface 46
4.3.6. Earthquakes 49
4.3.6.1. The crust 51
4.3.6.2. The mantle 52
4.3.6.3. The core 52
4.3.7. The Earth's atmosphere 52
4.3.8. The Earth's magnetic field 53
4.3.9. Earth summary 54
4.4. Mars 54
4.4.1. The surface of Mars 54
4.4.1.1. The highlands 55
4.4.1.2. The plains 57
4.4.1.3. Volcanic regions 58
4.4.1.4. Channels and canyons 60
4.4.2. Consequences of early water 62
4.4.3. Later missions 62
4.4.4. The atmosphere of Mars 65
4.4.5. Magnetism and Mars 66
4.4.6. Mars summary 66
Problem 4 67
5 THE MAJOR PLANETS AND PLUTO 68
5.1. Jupiter 68
5.1.1. The internal structure of Jupiter 68
5.1.2. Heat generation in Jupiter
5.1.3. The atmosphere of Jupiter 70
5.1.4. Jupiter's magnetic field 72
5.1.5. Jupiter summary 73
5.2. Saturn 74
5.2.1. The internal structure of Saturn 74
5.2.2. Heat generation in Saturn 75
5.2.3. The atmosphere of Saturn 75
5.2.4. Saturn's magnetic field 75
5.2.5. Saturn summary 76
5.3. Uranus 77
5.3.1. The internal structure of Uranus 78
5.3.2. Heat generation in Uranus 78
5.3.3. The atmosphere of Uranus 78
5.3.4. The magnetic field of Uranus 79
5.3.5. Uranus summary 79
5.4. Neptune 80
5.4.1. The internal structure of Neptune 80
5.4.2. Heat generation in Neptune 81
5.4.3. The atmosphere of Neptune 81
5.4.4. Neptune's magnetic field 81
5.4.5. Neptune summary 82
5.5. Pluto 82
5.5.1. Physical characteristics of Pluto 83
5.5.2. Relationship with Charon 83
Problem 5 84
6 THE MOON 85
6.1. The physical characteristics of the Moon 85
6.1.1. The distance, size and orbit of the Moon 85
6.2. Earth Moon interactions 88
6.2.1. The diurnal tides 88
6.2.2. The effects of tides on the Earth Moon system 89
6.3. Lunar and solar eclipses 90
6.3.1. Solar eclipses 90
6.3.2. Eclipses of the Moon 90
6.4. The lunar surface 91
6.4.1. The maria. 92
6.4.2. The highlands 93
6.4.3. B reccias 95
6.4.4. Regolith: lunar soil 95
6.5. The interior of the Moon 96
6.5.1. Gravity measurements 96
6.5.2. Lunar seismicity 98
6.5.3. The interior structure of the Moon 98
6.5.4. Heat flow and temperature measurements 98
6.6. Lunar magnetism 100
6.7. Some indications of lunar history 101
6.8. Moon summary 103
Problems 6 104
7 SATELLITES AND RINGS 105
7.1. Types of satellites 105
7.2. The satellites of Mars 105
7.3. The satellites of Jupiter 107
7.3.1. Io 107
7.3.2. Europa 109
7.3.3. Ganymede 110
7.3.4. Callisto 111
7.3.5. Commensurabilities of the Galilean satellites 112
7.3.6. The smaller satellites of Jupiter 113
7.4. The satellites of Saturn 114
7.4.1. Titan and Hyperion 114
7.4.2. Minas, Enceladus, Tethys, Dione and co-orbiting satellites 115
7.4.3. Rhea and Iapetus 117
7.4.4. Phoebe 117
7.4.5. Other small satellites 118
7.5. The satellites of Uranus 118
7.6. The satellites of Neptune 119
7.7. Pluto's satellite 120
7.8. Ring systems 120
7.8.1. The rings of Saturn 120
7.8.2. The rings of Uranus 122
7.8.3. The rings of Jupiter 122
7.8.4. The rings of Neptune 123
7.9. General observations 123
Problem 7 123
8 ASTEROIDS 124
8.1. General characteristics 124
8.2. Types of asteroid orbits 126
8.3. The distribution of asteroid orbits Kirkwood gaps 127
8.4. The compositions and possible origins of asteroids 128
Problem 8 131
9 COMETS 132
9.1. Types of comet orbit 132
9.2. The physical structure of comets 135
9.3. The Oort cloud 139
9.4. The Kuiper belt 142
Problems 9 143
10 METEORITES 144
10.1. Introduction 144
10.2. Stony meteorites 148
10.2.1. The systematics of chondritic meteorites 148
10.2.2. Achondrites 151
10.3. Stony irons 153
10.4. Iron meteorites 155
10.5. The ages of meteorites 159
10.6. Isotopic anomalies in meteorites 159
10.6.1. Oxygen in meteorites 159
10.6.2. Magnesium in meteorites 160
10.6.3. Neon in meteorites 162
10.6.4. Other isotopic anomalies 163
Problems 10 163
11 DUST IN THE SOLAR SYSTEM 164
11.1. Meteor showers 164
11.2. Zodiacal light and gegenschein 166
11.3. Radiation pressure and the Poynting Robertson effect 166
Problem 11 167
12 THEORIES OF THE ORIGIN AND EVOLUTION OF THE SOLAR SYSTEM 168
12.1 The coarse structure of the Solar System 168
12.2. The distribution of angular momentum 168
12.3. Other features of the Solar System 169
12.4. The Laplace nebula theory 170
12.4.1. Objections and difficulties 170
12.5. The Jeans tidal theory 171
12.5.1. Objections and difficulties 172
12.6. The Solar Nebula Theory 172
12.6.1. The transfer of angular momentum 173
12.6.2. The formation of planets 173
12.6.2.1. Settling of dust into the mean plane 174
12.6.2.2. Formation of planetesimals 174
12.6.2.3. Planets and cores from planetesimals 174
12.6.2.4. Gaseous envelopes 174
12.6.3. General comments 174
12.7. The capture theory 175
12.7.1. The basic scenario of the capture theory 175
12.7.2. Modelling the basic capture theory 175
12.7.3. Planetary orbits and satellites 176
12.7.4. General Comments 176
12.8. Ideas on the evolution of the Solar System 178
12.8.1. Precession of elliptical orbits 178
12.8.2. Near interactions between protoplanets 179
12.9. A planetary collision 179
12.9.1. The Earth and Venus 179
12.9.2. Asteroids, comets and meteorites 181
12.10. The origin of the Moon 181
12.10.1. Darwin's fission hypothesis 181
12.10.2. Co-accretion of the Earth and the Moon 182
12.10.3. Capture of the Moon 182
12.10.4. A single impact theory 183
12.10.5. Capture in a collision scenario 183
12.11. Other bodies in the Solar System 185
12.11.1. Mars and Mercury 185
12.11.2. Neptune, Triton, Pluto and Charon 185
12.12. Isotopic anomalies in meteorites 187
12.13. General comments on a planetary collision 189
Problem 12 189
TOPICS
A BASIC MINERALOGY 190
A.1. Types of rock 190
A.2. Types of minerals 191
A.2.1. Silicates 192
A.2.2. Carbonates 193
A.2.3. Oxides 193
A.2.4. Other minerals 194
A.3. Rock composition and formation 194
A.3.1. Igneous rocks 194
A.3.2. Sedimentary rocks 196
A.3.3. Metamorphic rocks 198
A.3.3.1. Thermal metamorphism 199
A.3.3.2. Pressure metamorphism 199
A.3.3.3. Regional metamorphism 200
Problems A 200
B GEOCHRONOLOGY RADIOACTIVE DATING 202
B.1. Comments on atomic structure 202
B.1.1. Nuclear structure 202
B.1.2. The emissions 203
B.2. The laws governing radioactive decay 204
B.2.1. The physical principles 204
B.2.2. A simple age measurement 205
B.2.3. Decay in a radioactive chain 205
B.2.4. Bifurcated decay 206
B.2.5. Age determination: the closure temperature 206
B.2.6. The isochron diagram 208
B.2.6.1. Rubidium —> strontium 208
B.2.6.2. Samarium —> neodymium 210
B.2.6.3. Rhenium —> osmium : lutetium —> hafnium 210
B.2.6.4. Uranium —> lead 210
B.2.6.5. Thorium —> lead 211
B.2.6.6. Potassium —> argon 211
B.2.7. The concordant diagram 211
B.3. Using nuclear reactors 213
B.3.1. Argon argon dating 213
B.3.2. Fission-track dating 214
Problems B 215
C THE VIRIAL THEOREM 216
Problems C 217
D THE JEANS CRITICAL MASS 218
D.1. An application of the Virial Theorem 218
D.2. From condensations to condensed bodies 220
Problem D 221
E FREE-FALL COLLAPSE 222
Problem E 224
F THE EVOLUTION OF PROTOSTARS 225
F.1. The Hertzsprung Russell diagram 225
F.2. The evolution of a protostar 227
Problems F 229
G THE EQUILIBRIUM OF STARS ON THE MAIN SEQUENCE 230
G.1. Conditions for modelling a main-sequence star 230
G.2. The pressure gradient 231
G.3. The included-mass gradient 232
GA. The luminosity gradient 232
G.5. The temperature gradient 232
G.6. Making models of stars 234
Problem G 234
H ENERGY PRODUCTION IN STARS 235
HA. Proton proton (p-p) reactions a classical view 235
H.2. A quantum-mechanical description 236
H.2.1. The distribution of proton relative energies 237
H.2.2. The rate of making close approaches 238
H.2.3. The tunnelling probability 238
H.2.4. The cross-section factor 239
H.2.5. The energy generation function 239
H.3. Nuclear reaction chains in the Sun 240
Problem H 242
I EVOLUTION OF STARS AWAY FROM THE MAIN SEQUENCE 243
I.1. An overview of the evolutionary path 243
I.2. Hydrogen-shell burning 245
I.3. Helium ignition and helium core burning 246
I.4. Hydrogen and helium shell burning 247
I.5. The evolution of higher mass stars 248
I.6. Final comments 250
Problem I 250
J THE CHANDRASEKHAR LIMIT, NEUTRON STARS AND BLACK HOLES 251
J.1. Some basic quantum mechanics principles 251
J.2. Degeneracy and white dwarf stars 251
J.3. Relativistic considerations 253
J.4. Neutron stars and black holes 254
Problems J 255
K PLANETS AROUND OTHER STARS 256
K.1. Planets around neutron stars 256
K.2. Effects of companions on the central star 256
K.3. Finding the speed and mass of the planet 257
K.4. The preliminary results of observations 260
K.4.1. Mass distributions 260
K.4.2. Characteristics of orbits 262
K.5. The constitution of the companions 263
K.6. Atmospheres 263
K.7. Possibilities of conditions for life 263
K.8. A final comment 264
Problem K 264
L SOLAR-SYSTEM STUDIES TO THE BEGINNING OF THE SEVENTEENTH
CENTURY 265
L.1. Views of the ancient world 265
L2. Nicolaus Copernicus 268
L3. Tycho Brahe 268
LA. Johannes Kepler 269
L.4.1. Kepler's determination of orbital shapes 270
L.5. Galileo Galilei 273
Problems L 275
M NEWTON, KEPLER'S LAWS AND SOLAR-SYSTEM DYNAMICS 276
M.1. Isaac Newton, Kepler and the inverse-square law 276
M.2. General orbits 277
M.3. Kepler's laws from the inverse-square-law force 279
MA. Establishing a Solar-System distance scale 281
M.5. The dynamics of elliptical orbits 281
M.6. Some special orbital situations 284
M.6.1. Parabolic paths of projectiles 284
M.6.2. Transfer orbits between planets 286
Problems M 287
N THE FORMATION OF COMMENSURATE ORBITS 288
O THE ATMOSPHERE OF THE EARTH 293
0.1. A simple isothermal atmosphere 293
0.2. The structure of the Earth's atmosphere 296
0.2.1. The variation of temperature with height 296
0.2.2. The upper reaches of the atmosphere 297
0.2.2.1. The exosphere 297
0.2.2.2. The thermosphere 301
0.2.2.3. The homopause 301
0.2.3. The lower reaches of the atmosphere 301
0.2.3.1. The mesosphere 301
0.2.3.2. The stratosphere and troposphere 302
0.3. The dynamics of the atmosphere 304
Problems 0 306
P THE PHYSICS OF PLANETARY INTERIORS 307
P.1. Introduction 307
P.2. Applying the Virial Theorem 307
RI The energies involved 307
P.3.1. The kinetic (degeneracy) energy 308
P.3.2. The electrostatic energy 308
P.3.3. The gravitational energy 309
P.3.4. The energies combined 309
P.4. Maximum radius 310
P.5. Conditions within a planet of maximum radius and mass 311
P.6. Specifying a planet: the planetary body 312
P.7. The minimum mass for a planetary body 312
P.7.1. The rigidity of a solid body 313
P.8. The internal structure of a planetary body 315
P.8.1. The crust 315
P.8.2. The maximum height of surface elevations 315
P.8.3. Hydrostatic equilibrium 315
P.8.4. Mantle and core 316
P.8.5. Variation of pressure and density with depth 316
P.8.6. Specifying K 317
Problems P 317
THE TRANSFER OF HEAT 318
Q.1. Conduction of heat in a solid 318
Q.1.1. The equation of heat conduction in a solid 319
Q.2. Comments on the description of fluid flows 320
Q.2.1. The fluid parameters 321
Q.2.2. The dimensionless parameters 321
Q.2.3. Physical interpretation: rearrangements 322
Problems Q 323
R SEISMOLOGY THE INTERIOR OF THE EARTH 324
R.1. The behaviour of planetary material for an impulsive release of energy 324
R.1.1. Waves without a boundary 324
R.1.2. Waves near a boundary surface 326
R.1.3. Full-body waves 327
R.2. Attenuation of seismic waves 328
R.3. Seismometers and seismographs 328
R.3.1. Travel times and seismic speeds 329
R.3.2. Reflection and refraction across a boundary 329
R.4. Seismic tomography 331
R.5. Long-term hydrostatic equilibrium of planetary material 331
R.6. The Adams Williamson method using earthquake data 331
R.7. Moment of inertia considerations 332
Problem R 333
S MOMENTS OF INERTIA 334
5.1. The moment of inertia of a uniform sphere about a diameter 334
S.2. The moment of inertia of a spherically symmetric distribution 336
S.3. The moment of inertia of a spheroid about the symmetry axis 336
Problem S 338
T THE GRAVITATIONAL FIELD OF A DISTORTED PLANET 339
T.1. The gravitational potential of a spinning planet 339
Problems T 340
U PRECESSION OF THE EARTH'S SPIN AXIS 341
U.1. The basic mechanism 341
U.2. The simple configuration 342
Problem U 343
V INTRINSIC PLANETARY MAGNETISM 345
V.1. Magnetic poles 345
V.2. Magnetic elements: isomagnetic charts 346
V.3. The form of the field 347
V.4. Analysing the field 351
V.5. The result for the Earth 352
V.5.1. The dipole approximation 353
V.5.2. The non-dipole component of the magnetic field 353
V.6. Time dependencies of the magnetic field 355
V.6.1. The dipole field 355
V.6.2. The non-dipole secular field the secular variation 356
V.6.3. Reversals of the direction of magnetization 358
V.6.4. Pole wander 358
V.6.5. Sea floor spreading 359
V.7. Magnetism of other Solar-System planets 361
V.8. Intrinsic magnetism of non-solar planets 363
Problem V 363
W MAGNETIC INTERACTIONS BETWEEN PLANET AND STAR 364
W.1. Transient magnetic components 364
W.2. The origin of the atmospheric fields 366
W.3. The solar wind 367
W.4. Coupling between plasma streams and magnetic fields 369
W.5. Effects of the solar wind 371
W.5.1. The effect on the Earth's field 371
W.5.2. The trapped particles 373
W.5.3. Whistlers 373
W.5.4. The plasma tail 373
W.6. The magnetospheres of other planets 375
W.6.1. The major planets 375
W.6.2. Examples of other planetary bodies 377
W.7. Motion through the interstellar medium 379
W.8. Companions to other stars 379
Problem W 379
X PLANETARY ALBEDOES 380
X.1. The brightness of Solar-System bodies seen from Earth 380
X.2. The equilibrium temperature of the planets 381
Problems X 382
Y THE PHYSICS OF TIDES 383
Y.1. The basics of the tide-raising mechanism 383
Y.2. Spring tides and neap tides 386
Y.3. The recession of the Moon from the Earth 387
Y.4. The magnitude of the mid-ocean tide 389
Y.4.1. Oscillations of fluid spheres 390
Problems Y 392
Z DARWIN'S THEORY OF LUNAR ORIGIN 393
AA THE ROCHE LIMIT AND SATELLITE DISRUPTION 395
AA.1. The Roche limit for fluid bodies 395
AA.2. The Roche limit for a solid body 396
AA.3. The disruption of a solid satellite 398
AA.4. The sphere of influence 400
Problems AA 401
AB TIDAL HEATING OF I0 402
AB.1. Elastic hysteresis and Q values 402
AB.2. Tidal stressing in Io 403
Problems AB 404
AC THE RAM PRESSURE OF A GAS STREAM 405
Problem AC 406
AD THE TROJAN ASTEROIDS 407
Problem AD 410
AE HEATING BY ACCRETION 411
AE.1. Models for the accretion of planets and satellites 411
AE.2. Accretion without melting 411
AE.3. Accretion with melting 412
AE.4. A more realistic initial thermal profile 414
Problem AE 415
AF PERTURBATIONS OF THE OORT CLOUD 416
AF.1. Stellar perturbations 416
AF.2. Perturbations by giant molecular clouds 419
AF.3. Perturbations by the galactic tidal field 420
AF.4. Conclusion 422
Problem AF 423
AG RADIATION PRESSURE AND THE POYNTING ROBERTSON EFFECT 424
AG.1. The force due to radiation pressure 424
AG.2. The Poynting Robertson effect 424
Problem AG 425
AH ANALYSES ASSOCIATED WITH THE JEANS TIDAL THEORY 426
AH.1. The tidal distortion and disruption of a star 426
AH.2. The break-up of a filament and the formation of protoplanets 428
Problem AH 429
AI THE VISCOUS-DISK MECHANISM FOR THE TRANSFER OF ANGULAR
MOMENTUM 430
Problem AI 431
AJ MAGNETIC BRAKING OF THE SPINNING SUN 432
AJ.1. Coupling of particles to field lines 432
AJ.1.1. The form of the magnetic field 432
AJ.1.2. The present rate of loss of angular momentum 433
AJ.2. The early Sun 434
Problem AJ 435
AK THE SAFRONOV THEORY OF PLANET FORMATION 436
AK.1. Planetesimal formation 436
AK.2. Planets from planetesimals 437
Problem AK 439
AL THE EDDINGTON ACCRETION MECHANISM 440
AL.1. The accretion cross section 440
Problem AL 441
AM LIFE ON A HOSPITABLE PLANET 442
AM.1. We are here 442
AM.2. Early life on Earth 443
AM.3. Chemical composition 445
AMA. General properties 445
AM.5. Instability due to radiation: role of an atmosphere 447
AM.6. Stability of the surface region 448
AM.7. How many planets might carry advanced life? The Drake equation 448
AM.8. Conclusion 449
AN THE ROLE OF SPACE VEHICLES 451
AO PLANETARY ATMOSPHERIC WARMING 456
AP MIGRATION OF PLANETARY ORBITS 459
AP.1. Deflection in a hyperbolic orbit 459
AP.2. Motion in an infinite uniform planar medium 461
AP.3. Resistance for a highly elliptical orbit 462
AP.4. Resistance for a circular orbit 462
Problem AP 463
AQ INTERACTIONS IN AN EMBEDDED CLUSTER 464
AQ.1. The initial conditions 464
AQ.2. Conditions for an interaction 465
AQ.3. Numerical calculations 465
Problem AQ 466
APPENDIX I 467
PHYSICAL CONSTANTS 474
SOLUTIONS TO PROBLEMS 476
REFERENCES 499
INDEX 501
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