Photoclinometry and Stereogrammetry of the Northern Martian Polar Layered Terrain
K. E. Herkenhoff (JPL), L. K. Fenton, B. C. Murray (Caltech)
The enigmatic layered terrain in the polar regions of Mars has been the subject of intensive study since its discovery during the Mariner 9 mission. It is now widely believed that the Martian polar layered deposits record climate variations over at least the last 10 to 100 million years, but the details of the processes involved and their relative roles in layer formation and evolution remain obscure (Thomas et al., 1992). Knowledge of the geology of the Martian polar deposits is essential in deducing the processes responsible for their formation and erosion, and the mechanisms by which climatic variations are preserved. Determining the topography of the polar layered terrain is an essential first step in understanding layered deposit stratigraphy and geologic history.
We will present the topography of an exposure of layered deposits at N, W, determined from Viking images by combining photoclinometry and stereogrammetry in the manner of Herkenhoff and Murray (1990). Stereo pairs exist for both spring and summer, allowing separation of topographic and albedo modulation of scene brightnesses. Photoclinometry is applied to a springtime image where a ubiquitous frost cover prevents changes in surface albedo from affecting slope calculations and allows topographic variations (terraces) to be clearly seen. Stereophotogrammetry provides absolute elevations that constrain the relative elevations established by photoclinometry. The combination of photoclinometry and stereophotogrammetry is a powerful tool for remotely determining detailed topography using stereo imaging data.
Herkenhoff, K. E. and B. C. Murray (1990). High Resolution Topography and Albedo of the South Polar Layered Deposits on Mars. J. Geophys. Res. 95, 14, pp. 511-514,529.
Thomas, P., S. Squyres, K. Herkenhoff, A. Howard, and B. Murray (1992). Polar Deposits on Mars. In Mars, University of Arizona Press, Tucson, pp. 767-795.