Loss of fine-scale surface texture in Viking Orbiter images and implications for the inferred distribution of debris mantles

A numerical, self-consistent model is defined for filtering out the effects of haze which cause a loss of fine-scale features in Viking Orbiter imagery of the Mars surface. Increased definition is necessary if the visual data is to serve for identifying terrain features which indicate the presence of volatiles such as ice. Crater images are used to calculate the change in atmospheric optical properties that accounts for alterations in the discriminability of crater features. Modulation transfer functions are developed for the image obscuration contributions of the atmosphere and the camera lens, thereby quantifying the smallest crater (6-7 pixels) that can be seen. The radiance of the viewed scene is modeled, and an atmospheric obscuration parameter is obtained as a function of the ratio of the atmospheric and surface obscuration contributions to the radiance at the detector. The contribution of the surface alone can then be identified. The model is applied in calculations of the total number of observed craters for comparisons with the expected number of craters, and to assess the potential for using the Viking cameras to characterize the geomorphic properties of various regions of the Mars surface.