These geologic maps of the north and south polar regions of Mars, extending to 55 north and south latitudes, overlap by 2 the geologic maps of the western and eastern regions, which extend to lat 57 . The map is the first of three in a series planned to cover the entire planet, portraying its lithology, stratigraphy, and structure. The text describes the major tectonic, volcanic, and fluvial episodes that have contributed to Mars' evolutionary history. The base used for compilation reflects improved imagery and photogrammetry and updated nomenclature. Relative ages of the units were established by stratigraphic and structural relations and by crater size-frequency distributions.
Line geometry is topologically clean.
During shaded relief portrayal, features on these bases were used to position details taken from Viking Orbiter pictures. The shading is not generalized and accurately represents the character of surface features. Information has been obtained from sources believed to be reliable, but its accuracy and completeness and the opinions based thereon, are not guaranteed. As every effort is made to provide accurate information in this database, USGS would appreciate it if users could call to our attention any errors that may occur by communicating with the contact person.