Say the word “dunes” and the image that likely comes to mind is the sort of features you’d see in the Sahara Desert; huge mounds of carmel-colored shifting sand. But on Mars, dunes take on an entirely different connotation, and with the orbital eyes of the HiRISE camera on the Mars Reconnaissance Orbiter, we’ve seen some pretty bizarre-looking dunes. Take the image above for example, a newly released photo of well-speckled dunes in Mars’ north polar region. In this image, taken during the northern spring season, the dunes and ground are still covered in seasonal frost. “The speckled appearance is due to the warming of the area — as the carbon dioxide frost and ice on the dunes warms, small areas warm and sublimate (turn from solid to gas) faster, creating small jets that expose/deposit dark sand and dust onto the surface,” writes Serina Diniega on the HiRISE website. “Notice that there are no spots on the ground between the dunes — that is because the ground stays more uniformly cold, unlike the darker dune sand.”
See below for more weird dunes on Mars.
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These dunes look as through someone has thrown a rippled blue-toned cloth across Mars’ surface. HiRISE is monitoring these dunes in Aonia Terra for changes such as gullies, which form over the winter from the action of carbon dioxide frost. This image was taken on January 18, 2012 here on Earth, but the season in on Mars where this was taken was late fall in the Southern hemisphere. “Frost is just starting to accumulate here, and is concentrated on pole-facing slopes and in the troughs between the meter-scale ripples,” wrote HiRISE Principal Investigator Alfred McEwen.
See more great images from Mars on the HiRISE website