Relating Polar Desert Polygonal Terrain Geometry and Sediment Distribution using Spatial Point Patterns
- Paper number
IAC-07-A5.I.-A3.I.B.04
- Author
Mr. Timothy Haltigin, McGill University, Canada
- Coauthor
Dr. Wayne Pollard, McGill University, Canada
- Coauthor
Dr. Pierre Dutilleul, McGill University, Canada
- Year
2007
- Abstract
Polygonal terrain is one of the most common landscape features found in Earth’s Arctic and Antarctic regions and is widely distributed throughout Mars’ high latitudes. Similar to those in terrestrial polar regions, Martian surficial polygons appear to be a result of thermal contraction cracking and are possibly associated with subsurface ice accumulation. At present, there is no method of estimating ground ice volumes beneath polygonal terrain via remotely sensed data. However, given the role of near-surface sediments in the formation of ice wedges and the overlying polygons, it is hypothesized that a more detailed analysis of surface morphology will provide insight into the structure of the ice wedges beneath. Through the Canadian Space Agency’s CARN program, we have begun a long-term study aimed at developing a relationship between ice wedge volumes and polygonal surface morphology through geophysical and image analysis techniques. The objective of the first phase of the project was to quantify the morphology of various polygonal terrains in the Canadian High Arctic and relate them to local sediment distribution. Subsequently, by comparing terrestrial and Martian polygon morphologies, it is possible that sub-pixel site characteristics on Mars’ surface can be inferred. Aerial photos were collected from a helicopter at study sites on Axel Heiberg Island and Devon Island. A high-resolution dGPS system was used to survey the sites such that the photos could be attributed with spatial coordinates. Surface sediment samples were quantified using a standard Wolman technique, which is used to produce a clast size distribution curve. Quantification of polygon geometrical parameters was derived from the photos using spatial point pattern analysis. A positive relationship was found between surface sediment size and polygon diameter, with larger sediment clasts being associated with larger polygons. Spatial point pattern analysis also revealed that trough intersection regularity, a proxy for the processes responsible for polygon formation, is a function of sediment distribution. The model parameters estimated for terrestrial spatial point patterns were compared to those obtained for a variety of Mars Orbiter Camera and Mars Reconnaissance Orbiter images of Martian polygonal terrain, some of which were shown to be geometrically comparable to the study sites. Future work will involve mapping and quantifying ice wedge volumes at each site using complementary geophysical tools. It is hoped that by relating ice content to sediment distribution, ground ice volumes can be estimated as a function of polygon morphology. This would provide a method for a first-order estimate of ice content beneath certain regions on Mars.- Abstract document