The dunes of Mars are in a complete state of flux, and none more so that Nili Patera. The most active dune field on Mars is always changing—and so it's constantly photographed by NASA's High Resolution Imaging Science Experiment.
That instrument is aboard NASA's Mars Reconnaissance Orbiter and it allows an image to the captured every six weeks. NASA explains:
By monitoring the sand dune changes, we can determine how winds vary seasonally and year-to-year. This observation is one of the more recent Nili images, acquired on March 1, 2014. Compared to an image acquired on Nov. 22, 2012, changes are obvious. The ripples on the dunes have moved, as well some of the dune boundaries, such as the one at upper left. New landslides on the central dune's lee face are apparent. Such changes, in just 16 months (and finer scale changes have been seen in just a couple of weeks), demonstrate the effectiveness of wind in modifying the Martian landscape.
The result is a constantly changing—and extremely photogenic—landscape. [NASA]