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These dunes are “barchan” dunes, which are also commonly found on Earth. Barchan dunes are generally crescent-shaped, with their “horns” oriented in the downwind direction. They have a steep slip face (the downwind side of the dune). Barchan dunes form by winds that blow mostly in one direction and thus are good indicators of the dominant wind direction. In this case, the strongest winds blow approximately north to south.