Martian dichotomy
geomorphological feature of Mars
The Martian dichotomy is a geomorphical feature of Mars, characterized by the contrast between the Southern and the Northern hemispheres. The two hemispheres' geography differ in elevation by 1 to 3 km. The average thickness of the Martian crust is 45 km, with 32 km in the northern lowlands region, and 58 km in the southern highlands.
The boundary between the two regions is quite complex in places. One distinctive type of topography is called fretted terrain. It contains mesas, knobs, and flat-floored valleys having walls about a mile high. Around many of the mesas and knobs are lobate debris aprons that have been shown to be rock glaciers.
Many large valleys formed by the lava erupted from the volcanoes of Mars cut through the dichotomy.
The Martian dichotomy boundary includes the regions called Deuteronilus Mensae, Protonilus Mensae, and Nilosyrtis Mensae. All three regions have been studied extensively because they contain landforms believed to have been produced by the movement of ice or paleoshorelines, though the latter interpretation has been questioned, with volcanic erosion proposed as an alternative.
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