2) How old it it?
3) Where is it?
4) What's it doing?
Fix Figure 9-02
B) Partially molten shell about 1000 km thick.
C) Thick crust (60 km) and lithosphere (1000 km).
Fix Figure 9-27
1) Highlands - light colored, heavily cratered old surface.
2) Mare (Latin for "sea") - Dark, smooth, "newer" surface, few craters.
The Simple Theories
2) Accretion (binary) theory - Moon accreted by itself when Earth formed.
3) Capture theory - Earth captured Moon after each had formed.
B) Early Period - Formed as a liquid and differentiated.
C) Volcanic Period - Lava flows filled in basins caused by impacts.
D) Inactive Period - "Geologically dead" for the last 3 billions years
Fix Figure 9-24
Based on Lunar regions with ages determined by radioisotopic dating, a relation between AGE and CRATER DENSITY has been established.
Steep rise in crater density for older lunar regions has lead to concept of
In the first 500 million years of the Solar System, many impacts on ALL planetary surfaces.
Based on lunar relation, AGES of other surfaces in the Solar System are estimated.
These rivers beds on Mars occur only in the heavily cratered regions on Mars, not in areas of low crater density. So, flowing water on Mars only occurred long ago as the evidence is only in the old surface regions of Mars.
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