06 August 2004
The springtime retreat of the north polar seasonal frost cap is progressing on schedule. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the state of defrosting north polar sand dunes just three days ago on 3 August 2004. Dark areas on the dunes are patches of bare sand; bright areas are remnants of frost deposited during the previous winter. Summer will arrive on 20 September 2004. These dunes are located near 76.3°N, 263.5°W. Their steepest slopes, known as the slip face of each dune, point toward the northeast (upper right), indicating wind transport of sand from the southwest (lower left). The image covers an area about 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.