NASA Mars HiRise Image:

Mars Reconnaissance Orbiter (MRO) spacecraft shows a sand dune field in a Southern highlands crater on the red planet. 

The sun lay only 5 degrees above the horizon when the spacecraft captured this image, producing deep shadows, with dune crests sticking up sharply into the sunlight. 

The bright patches which appear bluish in enhanced color arise from seasonal frost accumulating as this hemisphere approaches winter. 

Credit: NASA HiRISE