Terrestrial Planets
Sources of internal heat
Planetary Interiors
► If
everything else were equal
 The internal heat is proportional to the volume
of the planet, which goes as the cube of the
radius
 The rate of heat loss depends upon the area of
the surface, which goes as the square of the
radius
Net result
► The
ratio of stored heat versus cooling goes
something like R, the radius
► Thus, all else being equal, we expect the
interior of a larger planet to be warmer than
the interior of a smaller planet
Differentiated Interiors
Volcanism Mars
Olympus Mons
Volcanism Venus
Volcanism Earth
Plate Tectonics
Venus, tectonics yes, but not plate
tectonics
Mars: activity mostly in the past?
Valles Marineris
Valles Marineris
Moon: Geologically dead?
Mercury
► Similar
to the Moon, but with small lava plains
rather than the giant maria
Mercury: Cliffs created by crustal
movement
► Did
Mercury shrink as it cooled?