In this VIS image, taken by the NASA - Mars Odyssey Orbiter on February, 19th, 2014, and during its 54.773rd orbit around the Red Planet, we can see a small area of the North Polar Erg (---> Sea of Dunes), known as Olympia Undae. As the season changes from Spring to Summer, the Dunes surrounding the North Polar Cap, as you can see here, become darker, even though a few spots of Residual Water-Ice Frost can still be seen (on the lower portion of the frame).
Only the round and bright Feature located on the right (Dx) margin of the picture (in fact, an extremely interesting Surface Feature that we have already noticed in the past - see, for instance, the APOD of May, 5th, 2014 -, when other photos of this very same area were taken, even by other Orbiters), seems to remain - basically - unchanged (even though a few modifications of the shades of the Ice suggest that "something" might have actually happened - Melting? Sublimation?) during the entire Martian Year.
Unfortunately, we do not know what that Feature actually is (meaning that we do not know, as IPF, its True Nature), but our educated guess is that it could reasonably be a (relatively large) patch of Permanent Ice and Frost, resting in a medium-sized Surface Depression (an old Impact Crater maybe?), thick, compacted and protected well enough to resist to the Winds' Action (which is powerful in this very flat Martian Region) and then make it through the whole Martian Summer, when the temperatures of this Area (in a manner of speaking) considerably raise, without sublimating (or melting) completely.
Latitude (centered): 79,9626° North
Longitude (centered): 192,4560° East
This image (which is a crop taken from an Original Mars Odyssey Orbiter b/w and Map-Projected frame published on the NASA - Planetary Photojournal with the ID n. PIA 18501) has been additionally processed, magnified to aid the visibility of the details, 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.