One of the major extended-mission objectives for HiRISE has been to re-image parts of the Surface of Mars to look for changes. Such observations (like this one, obtained by the NASA - Mars Reconnaissance Orbiter on February 3, 2015) can tell us what kind of (Atmospherical and Geological - if any) Processes are still active today. This image was acquired as part of a series of frames aimed to look for Sand Movements in Meroe Patera, which is not far away from the active Sand Dunes of Nili Patera.
If you look at the picture carefully, you will be able to notice - among other interesting things - that Sand Dunes are missing Downwind (such as towards the left - Sx) of an Unnamed Impact Crater located near the lower center of the observation. Why? Well, this phenomenon happened because the Sand - pushed by strong Aeolian Activities, fell into the Crater itself and remained trapped.
Mars Local Time: 14:33 (Early Afternoon)
This picture (which is a NASA - Original Mars Reconnaissance Orbiter b/w and NON-Map-Projected frame identified by the serial n. ESP_039955_1875) has been additionally processed, reduced in size to fit the page, 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 Reconnaissance 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.