Passage to a Ringed World - NASA's History Office

More documents

Recommendations

Info

This Voyager 1 image shows Saturn’s “squashed” appearance — the planet’s equatorial bulge and flattened poles. THE RINGED WORLD 19
This cutaway diagram shows the basic structure of Saturn’s interior. 20 PASSAGE TO A RINGED WORLD the planet’s poles. As a result, Saturn’s equator is 60,330 kilometers from the center, while the poles are only 54,000 kilometers from the center. Almost 10 Earths can be lined up along Saturn’s equatorial diameter. The Mysterious Interior Low Density. To understand Saturn’s interior and evolution, we must apply our basic knowledge of physics to observations of Saturn’s volume, mass, gravity, temperature, magnetic field and cloud movement. The clues provided by this body of knowledge are not always easy to decipher, but as we gain more information on Saturn, we are more and more able to relate the pieces of the puzzle. Saturn has the lowest density of all the planets, because of its vast, distended, hydrogen-rich outer layer. In the early 1900s, we thought that the giant planets might consist entirely of gas. Actually, the giant planets contain cores of heavy elements like iron as well as other components of refractory and silicate compounds, and thus have several times the mass and density of Earth. Molecular Hydrogen Rock Saturn’s density is not uniform from its center to the surface — the density in the core is many times that of the surface. An understanding of this distribution is obtained through observations of planetary probes sent from Earth. Observations of the probe trajectories can be used to determine the density distribution throughout Saturn’s interior. The Rocky Core. Using data from the Voyager flybys, planetary scientists have put together a picture of Saturn’s interior. We believe that Saturn has a molten rocky core of about the same volume as Earth, but with three or more times the mass of Earth’s core. This increased density is due to gravitational compression resulting from the pressure of the liquid and atmospheric layers above the core. The rocky core is believed to be covered with a thick layer of metallic liquid hydrogen, and beyond that, a layer of molecular liquid hydrogen. The great overall mass of Saturn pro- duces a very strong gravitational field, and at levels just above the core the hydrogen is compressed to a state that is liquid metallic and conducts electricity. (On Earth, liquid hydrogen is usually made by cooling the hydrogen gas to very cold temperatures. On Saturn, liquid hydrogen is very hot, with temperatures of many thousands of kelvins, and is formed under several million times the atmospheric pressure found on Earth.) It is believed that this conductive liquid metallic hydrogen layer, spinning with the rest of the planet, is the source of Saturn’s magnetic field — turbulence or convective motion in this layer may be creating the field. A remarkable characteristic of Saturn’s magnetic field is that its axis of rotation is the same as that of the planet. This is different from that of the five other known magnetic fields, of Mercury, Earth, Jupiter, Uranus and Neptune. Present theory suggests that when the axes of rotation and magnetic field are aligned, the magnetic field cannot be maintained. Metallic Hydrogen
Page 1: Passage to a Ringed World The Cassi
Page 4 and 5: On the Cover: A collage of images s
Page 6 and 7: FOREWORD This book is for you. You
Page 8 and 9: ACKNOWLEDGMENTS This book would not
Page 10 and 11: Three separate images, taken by Voy
Page 12 and 13: descent to the surface. The Huygens
Page 14 and 15: address the challenges of the missi
Page 16 and 17: Participant Nations* * First flag i
Page 18 and 19: PROBING A MOON OF MYSTERY Huygens
Page 20 and 21: TOUR T18-3 TARGETED SATELLITE FLYBY
Page 22 and 23: SATURN CASSINI-HUYGENS MISSION SCIE
Page 24 and 25: Cassini-Huygens designed to determi
Page 26 and 27: In this diagram from his book, Syst
Page 30 and 31: An Extended Atmosphere From Liquid
Page 32 and 33: Haze layers are also observed above
Page 34 and 35: IN THE EYE OF THE BEHOLDER Taken fr
Page 36 and 37: This spectacular view of the edge o
Page 38 and 39: the interaction was described as a
Page 40 and 41: have a signature of a tone decreasi
Page 42 and 43: CONSTITUENTS OF THE TITAN ATMOSPHER
Page 44 and 45: The processes of plate tectonics an
Page 46 and 47: tan was accreting, it is possible t
Page 48 and 49: Surface Science. The highest resolu
Page 50 and 51: This enhanced Voyager 2 image shows
Page 52 and 53: Voyager 1 captured this striking im
Page 54 and 55: Prometheus and Pandora, two tiny sa
Page 56 and 57: In the stellar occultation experime
Page 58 and 59: scattering than are larger particle
Page 60 and 61: In fact, Saturn’s rings — as we
Page 62 and 63: The satellites of Saturn comprise a
Page 64 and 65: Before the advent of spacecraft exp
Page 66 and 67: The bright surface of Saturn’s mo
Page 68 and 69: Galilean satellites. Most of what i
Page 70 and 71: duced that one hemisphere is compos
Page 72 and 73: patches on the surface. Although it
Page 74 and 75: Artist’s conception of Ithaca Cha
Page 76 and 77: An artist’s rendition of Saturn
Page 78 and 79:
The MAPS Instruments Coordinated ob
Page 80 and 81:
field reverses direction across the
Page 82 and 83:
SATURN’S MAGNETIC FIELD Saturn’
Page 84 and 85:
Solar Wind Magnetosheath Titan neut
Page 86 and 87:
per atmosphere. Energetic particles
Page 88 and 89:
and plasma wave emissions from narr
Page 90 and 91:
CHAPTER 7 Space mission design aims
Page 92 and 93:
(SOI) propulsive maneuver to initia
Page 94 and 95:
the tour cannot continue. Of course
Page 96 and 97:
crease inclination to this value. T
Page 98 and 99:
This illustration shows the main de
Page 100 and 101:
discussed earlier) and data handlin
Page 102 and 103:
of the spacecraft! Below the oxidiz
Page 104 and 105:
• Opening or shutting thermal lou
Page 106 and 107:
management subsystem and the Probe
Page 108 and 109:
falls below its storage temperature
Page 110 and 111:
The Cassini-Huygens spacecraft stan
Page 112 and 113:
The Imaging Science Subsystem (ISS)
Page 114 and 115:
• Map the composition and thermal
Page 116 and 117:
cise distance between the surface f
Page 118 and 119:
• Study the interaction of the ma
Page 120 and 121:
• Study the erosional and electro
Page 122 and 123:
midway out on the magnetometer boom
Page 124 and 125:
The RPWS instrument will be used to
Page 126 and 127:
altitudes down to 40 kilometers abo
Page 128 and 129:
dex. A group of platinum resistance
Page 130 and 131:
CHAPTER 10 Mission operations are t
Page 132 and 133:
PLANETARY MISSION OPERATIONS Functi
Page 134 and 135:
two low-gain antennas 1 and will pr
Page 136 and 137:
During much of Cassini’s orbital
Page 138 and 139:
articulation control subsystem’s
Page 140 and 141:
AFTERWORD It has been said that in
Page 142 and 143:
Developments tied to the Cassini-Hu
Page 144 and 145:
APPENDIX A Command. A data transact
Page 146 and 147:
APPENDIX A 138 PASSAGE TO A RINGED
Page 148 and 149:
APPENDIX A Plasma wave. A wave char
Page 150 and 151:
APPENDIX A 142 PASSAGE TO A RINGED
Page 152 and 153:
APPENDIX B H O 2 + Water molecule w
Page 154 and 155:
APPENDIX C 146 PASSAGE TO A RINGED
Page 156 and 157:
APPENDIX D 148 PASSAGE TO A RINGED
Page 158 and 159:
APPENDIX D 150 PASSAGE TO A RINGED
Page 160 and 161:
APPENDIX F 152 PASSAGE TO A RINGED
Page 162 and 163:
APPENDIX F 154 PASSAGE TO A RINGED
Page 164 and 165:
APPENDIX F Peralta, F. and S. Flana
Page 168:
National Aeronautics and Space Admi
show all

Passage to a Ringed World - NASA's History Office

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?