AY 101 Lecture Notes - Lecture 12: Terrestrial Planet, Planetary Science, Plate Tectonics
Comparative Planetology: Terrestrials
While each of the terrestrial planets (the Moon can be considered one of these) has its
individual characteristics, many of their differences may be understood in the context of
their cooling history: Smaller objects cool more quickly than large objects. The smallest
terrestrial objects, the Moon and Mercury, froze solid relatively quickly. As a result, their
surfaces date to the time of this formation and preserved on these solid surfaces is a
history of events dating from very early times in the solar system. On the other hand,
the largest terrestrial planet, Earth, is still in the process of cooling, with heat flowing
outward from the hot core, driving convection in the mantle and producing the plate
tectonic phenomena at the surface.
All the terrestrial planets have a similar crust mantle core structure (see Figure 1). ‐ ‐
There is a general trend for density to increase with the size of the object (even when
corrected for compressional effects), indicating that a greater proportion of iron and
nickel is present in progressively larger planetary cores. Mercury, however, is an
exception to this rule; its iron core is far larger than expected for such a small planet.
Figure 1
Schematic cross section of the terrestrial planets.
Comparative Planetology: Gas Giants
Although the four gas giant planets are basically balls of hydrogen and helium gas and ‐
differ primarily only in mass, they have vastly different appearances. The progressive
change of appearance in these planets, from the spectacular orange reddish banding ‐
and belting of Jupiter to the deep blue, nearly featureless appearance of Neptune, may
be attributed to a single factor: their outer temperature. This temperature results from
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The smallest terrestrial objects, the moon and mercury, froze solid relatively quickly. As a result, their surfaces date to the time of this formation and preserved on these solid surfaces is a history of events dating from very early times in the solar system. On the other hand, the largest terrestrial planet, earth, is still in the process of cooling, with heat flowing outward from the hot core, driving convection in the mantle and producing the plate tectonic phenomena at the surface. All the terrestrial planets have a similar crust mantle core structure (see figure 1). There is a general trend for density to increase with the size of the object (even when corrected for compressional effects), indicating that a greater proportion of iron and nickel is present in progressively larger planetary cores. Mercury, however, is an exception to this rule; its iron core is far larger than expected for such a small planet.
