Mars: Structures & Vocabulary

Mars is a cold, dry terrestrial planet with a thin carbon-dioxide atmosphere, giant volcanoes, deep canyons, polar ice caps, widespread impact terrain, and abundant evidence that liquid water was more important in its ancient past. Its present environment preserves a record of major climate and geological change.

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.

Mars has a basaltic crust, enormous volcanoes, impact basins, canyon systems, polar caps, subsurface ice, and a thin atmosphere dominated by carbon dioxide. Its hemispheres differ strongly in elevation and crustal age. Present water is mostly frozen or bound in minerals, with transient atmospheric vapor and frost.