The extended-mission status of the Mars Reconnaissance Orbiter and the HiRISE camera has greatly increased our understanding of numerous active processes occurring on Mars. By taking carefully planned repeat images of surface, we now have an important record of how the surface evolves for a maximum of 5 Mars years.
This image shows the central peak in Porter Crater. Although there are no repeat images here we can infer several active geologic processes, based on morphologic evidence and lessons learned from past well-monitored sites. [More at link]