In this VIS image, taken by the NASA - Mars Odyssey Orbiter on December, 1st, 2013, and during its 53.077th orbit around the Red Planet, we can see, once again, the Erg (---> Sea/Ocean of Dunes) that surrounds the North Polar Cap of Mars. It is Springtime, now, at the North Pole (---> in the Northern Hemisphere of Mars) and the Dunes are starting to lose their Frost cover. As the season continues towards Summer, the Dunes will appear darker and darker, as the Frost sublimates.
Specifically, throughout the accurate observation (and, even more, after the colorization) of the landscape that is shown here, we are able to easily notice that, in this portion of the North Polar Erg (a portion that is positioned a little more towards the South of the Northern Hemisphere - as compared to the Latitude of the Region observed during the 53.076th orbit of the NASA - Mars Odyssey Orbiter), there has been more Frost lost from the Dunes, and this circumstance caused them to appear darker than the Dunes that were shown in yesterday's APOD.
Latitude (centered): 79,990° North
Longitude (centered): 128,365° East
This image (which is an Original Mars Odyssey Orbiter b/w and Map-Projected frame published on the NASA - Planetary Photojournal with the ID n. PIA 17866) has been additionally processed, magnified, contrast enhanced, Gamma corrected and then colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Mars Odyssey Orbiter and then looked down, towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.