Aerodynamic and vorticity erosion of Mars: Part II. Vortex features, related systems, and some possible global patterns of erosion
In Part I of this study, emphasis was placed on local and regional linear wind-erosion systems, particularly in the Tharsis and western Valles Marineris areas. In this, Part II, emphasis is placed on features interpreted to have developed or to have been enhanced by vorticity. Additional emphasis is placed upon correlations between character of topography and type of wind-eroded feature. Examples are: topography that causes vertical air movements promotes the development of centers of vorticity; thus, pits and craters are more abundant on top of and to the lee of plateau-like surfaces than on broad lowlands. In zones of strong confluence of air currents, such as the polar regions, large cyclic systems are developed, and they influence erosion over broad areas. Extremely high features such as the so-called volcanoes on Mars have caldera-like pits at their apices, within and around which there is abundant evidence of erosion by vorticity and interfacial-flow activity. Large centers of vorticity in these craters may also have created the low pressures necessary to establish the pressure gradients that are interpreted to have eroded the furrowed belt that nearly engirdles Mars. Comprehension of the relationship of furrowed landscape to centers of vorticity and other loci of low pressure permits development of data on both Martian wind patterns and on wind-erosion systems in general.