Thus, fracturing associated with the Tharsis bulge evidently has continued for much of the planet's history. Although fractures around 'Tharsis include the most prominent tectonic features on the planet, several fracture systems seem unrelated to Tharsis. Some fractures occur around old impact basins and are generally concentric to them. Especially prominent are the Nilae Fossae around the Isidis basin, but less distinct concentric graben and scarps are visible around the Argys and Hellas basins. Where the old cratered terrain is eroded, as in the fretted terrain, the erosion occurred preferentially along these directions.
Mare ridges are other possible examples of deformational features.
Such ridges are common on the sparsely cratered plains of Lunae Planum, Syria Planum, Hesperia Planum, and around the site of Viking Lander 1 in Chryse Planitia. In fact, Viking Lander 1 is believed to have landed on a ridge crest. The ridges on Mars have a striking resemblance to those on the Moon and are probably of similar origin. Terrestrial analogs have not been found, however, and their origin remains uncertain. Most of the cratered plains in the northern latitudes of Mars exhibit a polygonal pattern of fractures for which there is no terrestrial analog.