The surface of Mars 2. Uncratered terrains

Abstract

Mariner 6 and 7 photographs reveal two types of uncratered terrain on Mars. These are descriptively termed chaotic and featureless. Chaotic terrain is younger than cratered terrain and displays features strongly suggestive of slump and collapse. The speculation is offered that it may be an expression of geothermal developments within Mars that only recently have begun to affect the surface. Featureless terrain, identified only within the large circular area Hellas, is devoid of any discernible topographic forms larger than the limit of resolution, about 500 meters. Manner 7 data indicate that Hellas is a topographically low and structurally old basin. Smoothness of its floor could be the product of a recent event or of continuous processes that obliterate craters. Local processes of high efficacy, unusual surface materials, or both, are probably involved. Through its chaotic terrain the martian surface displays a development that does not seem to be recorded, at least in the form of preserved recognizable evidence, on the moon or earth.