Defrosting North Polar Dunes (Original NASA/MGS/MSSS b/w Frame)

Caption NASA originale:"This MGS-MOC image shows a portion of a sand dune field in the North Polar Region of Mars. The dunes are covered with frozen CO2, which accumulated over the Autumn and Winter months in the Northern Hemisphere. During the Spring, the time at which this image was acquired, the CO2 begins to sublime away, going directly from solid to gas, just as dry ice does here on Earth.
The dark spots, streaked by blowing winds, may be places where the frost has been removed (exposing underlying dark sand), places where the grain size or roughness of the frost has increased (increasing shadowing due to the change in texture), or both".

Location near: 79,7° North Lat. and 148,3° West Long.
Image width: ~3 Km (~1,9 mi)
Illumination from: lower left
Season: Northern Spring