Volcanic flows have been suggested as explanations for many of the varied terrain types on mars, including kilometers of layered rocks in the Valles Marineris. In the Cydonia region, volcanic flows are not likely as land- forming mechanisms. There appear to be no significant volcanic sources in this region nor can the distinctive erosion morphologies of many of the landforms in Cydonia be easily attributed to volcanism. To the contrary, some of the erosion appears to be structurally controlled, perhaps by faults, layered rocks or even folded sediments. Furthermore, evidence for both erosion and deposition by water is strong in Cydonia.
Evidence also exists for both precipitation and surface runoff.
Apparent rills are found on some of the landforms and they appear markedly similar to rill types found in sedimentary terrains in the western United States. Still, caution must be taken when using strict earth-based analogies for martian terrains. Taking that into consideration and despite strong evidence for water in Cydonia, we propose that the typical tributary stream networks common on earth may not be as common on mars on the basis of the different gravitational field strength. Specific crater features found include, a smooth, flat floor surface, high albedo floor surface, a reflection of the floor surface on the crater wall, no apparent ejecta apron, and steep crater walls. Several possible explanations for the presence of water ice in the floor of the subject crater are presented.