Analysis of the Argyre Planitia (Mars) Sinuous Ridges Using Early MRO Images

Southeastern Argyre Planitia hosts a suite of dendritic and braided sinuous ridges. Here we use imagery from the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) camera and Context Camera (CTX) to constrain formation processes of the ridges. HiRISE images resolve large boulders, up to ~8 m in diameter, on the ridges; however, it is unclear if the boulders, particularly those that appear more angular, may be eroding out of layers of indurated material or represent transported particles. Well defined layers observed in one of the ridges are quasi-horizontal and, in general, longitudinally continuous. Frequent transitions in ridge crest morphology from sharp-crested to rounded or flat-topped are evident. In several locations, ridges also appear to lie in shallow troughs that are several kilometers in width and mantled with finer sediments. Topographic profiles across and along the three ridges imaged by HiRISE and CTX are derived from Mars Orbiter Laser Altimeter (MOLA) data and reveal that the ridges generally trend in a slope-parallel direction, but cross over low intrabasinal topographic divides. If the regional topography has remained stable, the tendency for the ridges to cross topographic highs suggests formation by pressurized flow rather than gravity driven flow (open river channels). Altogether, the Argyre ridge characteristics are consistent with sub-ice fluvial processes and most likely represent terrestrial esker-like features. Terrestrial eskers have similar morphologies and distributions and may cross topography, contain layers, and lie within troughs, often referred to as Nye channels, which form from subglacial meltwater erosion. The nature of some eroding beds within the Argyre ridges suggests a possible induration process. We present a further analysis of the characteristics of the Argyre ridges and the potential environment in which the ridges formed.