More and more frequently in recent years, I see images from space that simply take my breath away - this image from Mars did just that. I'm not sure what it is about these rolling dunes on Mars that struck me - maybe it's that they are so similar to dunes on Earth, yet they exist millions of kilometers away on an alien world. Maybe it's just that they are beautiful.
You can download this image in multiple resolutions here.
From the University of Arizona post:
Dune fields located among canyon wall slopes are also known as “wall dune fields” and are further identified as either climbing or falling. Falling dunes are defined as large bedforms with lee faces on the downhill side—indicating that this is the direction of their migration—and on moderate slopes greater than 10 to 12 degrees. (A lee face is the the down-wind side of a dune.)
On Earth and Mars, these types of dunes are largely controlled by what is called “microtopography.” Physical obstacles can accelerate and decelerate airflow, create turbulence, potentially enhancing erosion, deposition, and/or transport of dune sediment.
This class of dune morphology is relatively rare across Mars. However, falling dunes (like these) and climbing fields are frequently located among the spur-and-gully walls in the Melas and Coprates chasmata (see the paper here). Here is one example, of active falling dunes on this large massif in east Coprates Chasma.
These dunes were imaged using the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter. HiRISE is the most powerful camera ever sent to another planet, and has been imaging the surface of Mars since 2006. HiRISE has witnessed avalanches happening, new impact craters occurring, and dark flows which may (or may not) be briny water. Hundreds of scientific papers have been published using HiRISE data.
You can view HiRISE imagery of the surface of Mars using the free HiView app here.