Engineering topics
Spohn, Tilman
Publications and source records attributed to Spohn, Tilman.
A Network of Geophysical Observatories for Mars
For the past 30 years there has been a strong consensus within the international scientific community in favor of sending a network of geophysical landers to Mars to characterize the near-surface weather and climate, determine the large-scale atmospheric dynamics and explore the interior structure and composition. Despite this scientific support, there has been an unbroken string of proposed missions over the past fifteen years which have failed for programmatic reasons to progress beyond the design stage (Mars Network Mission, MESUR, Marsnet, InterMarsnet, NetLander). In this presentation, we review the scientific rationale and technical requirements for such a mission, and discuss current activities aimed toward its implementation.
Thermal equilibration of the earth following a giant impact
A thermal evolution model for the cooling of a terrestrial planet, a prescribed fraction of which is melted during a giant impact, is described. Two model geometries are considered, one having a laterally inhomogeneous distribution of melt and solid through a mega-crater geometry and the other having a global magma ocean. It is found that almost the whole planet may melt if the impact originally melted half of the planet and if the first melt temperature was double a typical planet melting temperature. For reasonable choices of parameter values it is determined that thermal equilibration of the earth occurs on a time-scale of 1 to ten million years.
Thermal history of Mars and the sulfur content of its core
A model for thermal evolution of the Martian mantle and core and for the evolution of the Martian magnetic field is developed by expanding the planetary thermal history model of Stevenson et al. (1983) and using the energy balance equations from that work. Several parameter values are chosen differently from those of the Stevenson model, including those for mantle density, core radius, core density, central pressure, and pressure at the core-mantle boundary. The model is further modified to allow calculations of lithosphere thickness through time. According to the model, the core contains a light alloying constituent, assumed to be sulfur. The results of calculations show that a small Martian magnetic field can be generated by a weakly convecting liquid core.
Thermal histories, compositions and internal structures of the moons of the solar system
Thermal evolution models of satellites are discussed with emphasis placed on the fundamental physical processes common to all planetary bodies. A comparison is made between the different evolutionary tracks followed by individual satellites. Consideration is given to the compositions and structures of satellites, heat sources, relevant thermal and mechanical properties of the materials in satellite interiors, and heat transfer mechanisms. Thermal history scenarios are presented for the majority of the satellites of the solar system and these are related to the constraints imposed by surface geology.