Terrestrial Planets and Moon Summary

Terrestrial Planets – Surfaces

• Earth has craters, but fewer than the Moon due to active geological processes.

Moon – Maria Creation

• Many maria are giant impact basins; lava filled these basins after impacts.

Moon – Near and Far Sides

• Large maria are absent on the Moon's far side.

Moon – Interior

• Off-center core, low density suggests small metal core; solid mantle; thick ridged crust; thinner crust facing Earth.

Terrestrial Planets – Interiors

• All terrestrial planets formed hot and differentiated due to melting.

Differentiation

• Heavy materials sink, lighter materials rise when heated above 1300 K.

Active vs. Dead Planets

• Active planets retain geological activity (e.g., Earth); dead planets lack heat and activity (e.g., Moon).

Origin of the Moon – Theories

• Theories include "sister," "capture," and "giant impact" theories; the giant impact theory is most widely accepted.

Giant Impact Theory

• Suggests a Mars-sized object, Theia, collided with Earth, forming the Moon.

Evidence for Giant Impact

• Similar composition and orbital properties of the Moon support the giant impact theory.

Moon and Water

• Water exists on the Moon as ice; confirmed by missions like Chandrayaan-1 and LRO/LCROSS.