Mars: Physical Mechanisms

Mars has a rocky crust and mantle, a metallic core, a thin atmosphere, two small moons, and strong hemispheric geological contrasts. The southern highlands are older and heavily cratered, while much of the northern hemisphere is lower and smoother. The Tharsis volcanic province contains enormous volcanoes, and Valles Marineris forms a vast canyon system.

Mars's lower gravity and lack of active plate tectonics allowed volcanoes to remain over long-lived mantle sources and grow to extreme size. Its small mass also helped the interior cool more quickly than Earth's, weakening the global magnetic dynamo. Atmospheric loss and cooling reduced surface pressure and temperature, making stable liquid water difficult at the surface today.

Orbiters, landers, and rovers have mapped channels, deltas, layered sediments, hydrated minerals, volcanic landforms, and polar deposits. Martian meteorites preserve atmospheric gas signatures, and rover chemistry shows past environments that interacted with liquid water. Crustal magnetization records an ancient global magnetic field that later disappeared.

Early volcanic outgassing and a denser atmosphere could support warmer episodes, while atmospheric escape, declining interior heat, and loss of dynamo protection contributed to long-term drying. Dust cycles reshape atmospheric heating, and obliquity variations redistribute ice over geological time.