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Planetary Exploration, 1968-1975; Report of a Study by the Space Science Board, Washington, D.C., June 1968 (1968) / Chapter Skim
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Planetary Dynamics and Interiors
Pages 35-41

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From page 35...
... Spacecraft missions of interest to the study of planetary dynamics and interiors that appear practically feasible in the mid-1970's (listed in order of distance from the Sun) are: Mercury fly-by Venus orbiter Mars orbiter Mars lander Asteroid probe Short-period-comet probe Jupiter fly-by The plan of this chapter is to discuss each of the bodies to which these experiments pertain and then to take up the question of priorities.
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From page 36...
... Hence Venus furnishes a valuable test of theories, both of the Earth's interior and of the origin of terrestrial planets: any acceptable theory must explain why Earth and Venus are different. Simple extrapolations from the Earth to Venus inevitably result in contradictions: a higher surface temperature indicates a hotter, weaker, and more rapidly creeping interior, which is consistent with the viscous decay time but inconsistent with the strength implied by the spin-orbit coupling.
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From page 37...
... A more sensitive magnetometer in a magnetically clean spacecraft is technically feasible; a feeble dipole moment detected by this instrument might be taken to indicate the presence of a small fluid core in Mars. Planetary heat flow is a difficult question, one that is unlikely to be answered by an early generation of Mars landers because of the weight and complexity of equipment needed to implant heat sensors beneath the surface.
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From page 38...
... Theoretical and model study ought to be able to provide fairly good estimates of the noise produced by ground-coupling and direct instrument coupling from the wind. We may hope that orbital photography in an early Mars mission and numerical-theoretical work on the atmosphere will provide closer estimates of wind velocities near the surface.
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From page 39...
... There is still much to be accomplished by ground-based astronomical techniques. Those that contribute most importantly to the study of planetary dynamics and interiors are radar measurements (which yield orbit and spin data as well as surface properties, including variations in topographic heights)
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From page 40...
... Because of its excessive surface temperature and thick atmosphere, however, the only useful measurements that appear feasible are determinations of the variations of the gravitational field from satellite orbit perturbations. Such determinations, preferably using orbiters of differing inclination, should yield significant boundary conditions on the mechanical and thermal state of the interior.
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From page 41...
... Venus Orbiter Surface photography IR radiometry Tracking transponder (3 months in orbit) Photography IR radiometry Tracking, 3 mos.
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Key Terms

  • heat flow
  • gravitational field
  • magnetic field
  • venus orbiter
  • surface photography

  • planetary interiors
  • surface temperature
  • boundary conditions
  • terrestrial planets
  • planetary heat

  • orbiter mars
  • mars orbiter
  • mars landers
  • mass distribution
  • mass density

  • internal mass
  • internal activity
  • heat balance
  • provide significant
  • radiometry tracking

  • emission observations
  • versus depth
  • viscous decay
  • decay time
  • chemical composition

  • tracking transponder
  • dipole moment
  • precessional torques
  • mars mission
  • mars lander


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