The Geologic History of Terby Crater: Evidence for Lacustrine Depsoition and Dissection by Ice

Introduction: The geology of Terby Crater (28S, 287W), located on the northern rim of Hellas impact basin on Mars, is documented through geomorphic and stratigraphic analyses using all currently released visible and thermal infrared image data and topographic information. This large (D=164km), Noachian-aged [1] crater has a suite of geomorphic units [2] and landforms including massive troughs and ridges that trend north/northwest, sedimentary layered sequences, mantled ramps that extend across layered sequences, avalanche deposits as well as bowl-like depressions, sinuous channels, scoured-looking caprock, viscous flow features, fans, esker-like ridges, arcuate scarps and prominent linear ridges that may be indicative of past and present ice flow (Figure 1). The variety of the landforms within Terby and the surrounding area suggests that spatially and temporally varying geologic and geomorphic processes were responsible for the formation and modification of these features, perhaps as a response to changes in climate resulting from quasi-cyclical orbital variations [e.g. 3].