Topography and stratigraphy of Martian polar layered deposits

Abstract

Topography and stratigraphy of young sediments in the Martian north polar region are being studied from high-resolution Viking Orbiter images to test and constrain theories of terrain evolution driven by cyclical climate change. Several steepened slopes upon which layers are exposed in section were found to have local relief of 200 to 800 m and slopes ranging from 1 to 8°. First attempts to calculate average layer thicknesses from portions of sections yielded results ranging from 14 to 46 m, linearly correlated with slope. In some cases, under the assumption of short-range lateral continuity, a greater number of layers was inferred to be present than was actually resolved on a particular section. When apparent layer thickness are revised accordingly, the correlation with slope is destroyed. We conclude that images of the shallowest-sloping sections of layered deposits should yield the most stratigraphic information, and layers thinner than 14 m may occur; indeed, they may even be common or typical. Because of the sensitivity of summer frost distribution to local slope and other properties of exposed strata, interseasonal comparisons of images promise to enhance the capability to detect layers and differentiate them by material properties.