Spaceborne visible and thermal infrared lithologic mapping of impact-exposed subsurface lithologies at the Haughton impact structure, Devon Island, Canadian High Arctic: Applications to Mars

摘要

This study serves as a proof-of-concept for the technique of using visible-near infrared (VNIR), short-wavelength infrared (SWIR), and thermal infrared (TIR) spectroscopic observations to map impact-exposed subsurface lithologies and stratigraphy on Earth or Mars. The topmost layer, three subsurface layers and undisturbed outcrops of the target sequence exposed just 10 km to the northeast of the 23 km diameter Haughton impact Structure (Devon Island,. Nunavut, Canada) were mapped as distinct spectral units using Landsat 7 ETM+ (VNIR/SWIR) and ASTER (VNIR/SWIR/TIR) multispectral images. Spectral mapping was accomplished by using standard image contrast-stretching algorithms. Both spectral matching and deconvolution algorithms were applied to image-derived ASTER TIR emissivity spectra using spectra from a library of laboratory-measured spectra of minerals (Arizona State University) and whole-rocks (Ward's). These identifications were made without the use of a priori knowledge from the field (i.e., a "blind" analysis). The results from this analysis suggest a sequence of dolomitic rock (in the crater rim), limestone (wall), gypsum-rich carbonate (floor), and limestone again (central Uplift). These matched compositions agree with the lithologic units and the pre-impact stratigraphic sequence as mapped during recent field studies of the Haughton impact structure by Osinski et al. (2005a). Further conformation of the identity of image-derived spectra was confirmed by matching these spectra with laboratory-measured spectra of samples collected from Haughton. The results from the "blind" remote sensing methods used here suggest that these techniques can also be used to understand subsurface lithologies on Mars, where ground truth knowledge may not be generally available.