Terrestrial PlanetsTerrestrial Planets

Sources of internal heatSources of internal heat

Planetary InteriorsPlanetary Interiors

► If everything else were equalIf everything else were equal The internal heat is proportional to the The internal heat is proportional to the

volume of the planet, which goes as the volume of the planet, which goes as the cube of the radiuscube of the radius

The rate of heat loss depends upon the The rate of heat loss depends upon the area of the surface, which goes as the area of the surface, which goes as the square of the radiussquare of the radius

Net resultNet result

►The ratio of stored heat versus cooling The ratio of stored heat versus cooling goes something like R, the radiusgoes something like R, the radius

►Thus, all else being equal, we expect Thus, all else being equal, we expect the interior of a larger planet to be the interior of a larger planet to be warmer than the interior of a smaller warmer than the interior of a smaller planetplanet

Differentiated InteriorsDifferentiated Interiors

Volcanism MarsVolcanism Mars

Olympus Mons

Volcanism VenusVolcanism Venus

Volcanism EarthVolcanism Earth

Plate TectonicsPlate Tectonics

Venus, tectonics yes, but not Venus, tectonics yes, but not plate tectonicsplate tectonics

Mars: activity mostly in the Mars: activity mostly in the past?past?

Valles MarinerisValles Marineris

Valles MarinerisValles Marineris

Moon: Geologically dead?Moon: Geologically dead?

MercuryMercury

► Similar to the Moon, but with small lava Similar to the Moon, but with small lava plains rather than the giant mariaplains rather than the giant maria

Mercury: Cliffs created by Mercury: Cliffs created by crustal movementcrustal movement

►Did Mercury shrink as it cooled?Did Mercury shrink as it cooled?