Noachian named after Noachis Terra
Description and name origin
The Noachian System and Period is named after Noachis Terra (lit. "Land of Noah"), a heavily cratered highland region west of the Hellas basin. The type area of the Noachian System is in the Noachis quadrangle (MC-27) around 40°S 340°W. At a large scale (>100 m), Noachian surfaces are very hilly and rugged, superficially resembling the lunar highlands. Noachian terrains consist of overlapping and interbedded ejecta blankets of many old craters. Mountainous rim materials and uplifted basement rock from large impact basins are also common. (See Anseris Mons, for example.) The number-density of large impact craters is very high, with about 200 craters greater than 16 km in diameter per million km2. Noachian-aged units cover 45% of the Martian surface; they occur mainly in the southern highlands of the planet, but are also present over large areas in the north, such as in Tempe and Xanthe Terrae, Acheron Fossae, and around the Isidis basin (Libya Montes).
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