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

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?