| Shorelines and alluvial fans are valuable indicators of Martian paleoclimate. Shorelines and alluvial fans imply the presence of stable, standing surface water. Shorelines have been inferred in a variety of Martian settings. Here I present a quantitative analysis of shorelines on Mars by estimating the wave energy field and how it would erode shorelines under Martian planetary conditions. The lower gravity and air pressure combined with the lack of tides on Mars affect the shorelines. Given a reasonable range of shore slopes and bedrock parameters, it is very difficult to form distinctive shoreline features. I conclude that many of the features previously interpreted as shorelines were not formed by standing, open water, but instead by an alternate formation mechanism, such as ice-shore interactions. To study alluvial fans, I performed a global survey using THEMIS IR 100 m/pixel images. Large alluvial fans on Mars form nearly exclusively in medium-sized impact craters. Most alluvial fans are regionally clustered in southern Margaritifer Terra, southwestern Terra Sabaea, and southwestern Tyrrhena Terra. The uniformity in the preservation of fans indicates that the clustering is a function of formation rather than preservation. The local formation (within a crater) of alluvial fans is not dependent on orientation or association with existing areas of high topography. I hypothesize that the impact process itself may contribute in some key way to localized formation within the crater, while climate patterns may drive the regional groupings. Ultimately, through careful geomorphic and geophysical studies, it is possible to use these features, in combination with others, to understand the climate history of Mars. |
