Martian surface and crust: Review and synthesis

Mariner 9 data and earlier data are combined to investigate the nature of the classical markings on Mars. This leads to a model of crustal evolution and structure. Combination of radar and spectrophotometric data strengthens earlier evidence for petrologic distinctions between surface materials in dark and light regions. The classical surface markings are a complex result of three influences: (1) availability of two types of rock material transportable by wind, (2) topographic control of deposition, and (3) prevailing winds producing quasipermanent preferential deposition patterns. The crust, especially in the Tharsis region, bears strong evidence of mantle-induced uplift of a type recognized on Earth as long ago as 1939. Such uplifts have obliterated ancient craters, caused fractures, and graben systems such as the Coprates canyon, and resulted in intense volcanism. This evidence, combined with an apparent bimodal hypsometric diagram, indicates Mars has current or recent mantle activity sufficient to disturb the crust, aid in petrologic differentiation, and cause development of protocontinental units, but insufficient to cause full-fledged continental drift or fold-causing plate collisions as are common on Earth.