Mariner 9 observations of the surface of Mars in the north polar region

The recession rate of the north polar cap, as monitored by Mariner 9, was not significantly different than has been observed from earth in the past. Thus, the dynamic planet-wide dust storm does not seem to have had a noticeable effect on the thickeness of the CO2 deposit which developed during the standard mission. The dominant role of local topography in controlling the configuration of the retreating cap is confirmed. At narrow-angle resolution the retreating frost has high-lighted topographic detail that may represent Martian polar eolian deposits. At wide angle resolution the topography of the smooth plains, rugged etch pitted terrain, and complex central polar deposits is emphasized by the frost.