Lecture Notes:
Models
Introduction
Having examined the two objects which we know the best, we find
they are very different. We have developed several models, however,
which seem to apply to both Earth and Moon. I summarize those models
here before we try applying them to other objects in the solar
system.
Structure: Differentiation
- heavy elements settle to center
- happens when molten
Structure: Solidification
- smaller objects cool faster
- smaller objects may be solid all the way through
Structure: Magnetic field
- To have a magnetic field, we need:
- liquid region inside planet
- rotation of planet
- does not explain why Earth's magnetic field is tilted and
flips
Surface: Albedo
- albedo = fraction of light reflected
- high albedo = ice
- moderate albedo = clouds or water
- low albedo = rock
Surface: Erosion
- surface can be changed by
- water erosion
- wind erosion
- chemical reactions
Atmosphere: Composition
- escape speed determines is a particular type of gas (hydrogen,
oxygen, ...) is kept
- if planet is hot enough, lighter elements will escape
- presence of life enhances nitrogen and oxygen in
atmosphere
Atmosphere: Circulation
- circulation patterns arise from
- convection - hot air rises
- rotation of planet
- leads to cells in atmosphere
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