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Where Trade Routes Meet, a Mesa Rises
Credit: NASA/JSC

Gebel (or Mount) Edmonstone is a flat-topped mesa located near the Dahkla Oasis south of Cairo, Egypt. The Oasis is a historically important meeting place of several trade routes connecting different regions of Egypt and Sudan. Gebel Edmonstone is a remnant of an eroding scarp that extends for over 200 kilometers (125 miles) east-southeast to west-northwest (visible in the upper left corner of the image). The flat caprock of both the scarp and Mount Edmonstone is chalky limestone underlain by fossil-bearing shale and fine-grained sedimentary rocks.

Digital astronaut photographs can be processed in similar fashion to other multispectral remotely sensed data to maximize information content. This astronaut photograph has been stretched to enhance color variations in the various rock and soil units. The color variations reflect differences in composition (or weathering) of the various rock units. The limestone unit capping Gebel Edmonstone and the adjacent scarp ranges from white to gray in color, while the underlaying fine-grained sedimentary layers are blue-gray.

Hillslope pathways for sediment movement downslope are clearly visible as brown to tan streamers originating from Gebel Edmonstone. Barchan dune fields are also visible in this color-enhanced image, and are distinct due to their mineralogical composition. Evaporite deposits are bright white, while vegetated portions of the Oasismostly agricultural fieldsare dark blue-black. This additional information obtained from image enhancement can be used for geologic mapping and investigation of surficial processes operating in the region.