Active Mars Geology

Researchers using a high resolution camera on the Mars Reconnaissance Orbiter have discovered that huge sand dune fields in the northern polar region of the planet can change relatively quickly-- in two Martian years, for example, which equals about four Earth years.

They explain the changes by noting the actions of carbon dioxide and wind. During the Martian winters, carbon dioxide is stable in frozen form. It exists atop and within dunes, adding to their stability. In the spring, however, the carbon dioxide changes directly into gas, thus leaving voids in the dunes, and weakening their overall structure. Thus, when winds pick up, the sand can be blown to shape new dunes.

In a narrow sense, therefore, Mars is geologically active now. Whether it is in a broader sense, one that would include marsquakes, water acting in some way to shape the planet even today, or active vulcanism remains to be seen.