Ice Keel Scour Marks on Mars: Evidence for Floating and Grounding Ice Floes in Kasei Valles

摘要

We present new observations from analyses of Mars Global Surveyor Mars Orbiter Camera images of surficial Martian features interpreted to be the result of interactions between the keels of floating ice masses on submerged sediment. There are two types of features made by grounding ice masses: narrow, intersecting curvilinear trough-like features are ice keel scour marks and are present in large reaches of the Kasei Valles and parts of the Echus Chasma system (Figure 1) and; irregular to sub-circular areas, outlined by small ridges, that represent grounding pits made by large, flat-bottomed ice floes. We base our interpretations on the morphology and local patterns of individual scour marks and ice floe grounding pits. We compare these Mars observations with identical contemporary ice keel grounding structures forming in an analogous environment in the St. Lawrence River on earth.