Geomorphic processes in the Argyre-Dorsa Argentea region of Mars

Among many indications of possible ancient Martian galciation are sinuous eskerlike ridges in southern Argyre Planitia and the Dorsa Argentea region. But, in photogeology, other interpretations are always possible, and what appears eskerlike to one set of eyes may appear quite different to another. Interpretations of these ridges are about as numerous as observers, who collectively have suggested nine distinct hypotheses. Martian sinuous ridges have been interpreted as wrinkle ridges, lava flows, igneous dikes, clastic dikes, linear sand dunes, spits or bars, examples of inverted stream topography, or glacial crevasse fill. With Mars Observer en route to Mars, the prospects for a narrowing of the debate are bright. The esker hypothesis will gain support if Mars Observer images show that the ridges contain boulders, that the ridges are layered and contain channel structures, that the ridges are modified by thermokarst, or that the ridges occur in close, logical associations with other glacial landforms such as flutes, oriented grooves, and moraines. In the meantime, the evidence presented below bolsters the esker hypothesis, challenges certain alternative ideas, and draws a tentative geomorphic connection between the sinuous ridges of Argyre and those of Dorsa Argentea.