At www.physorg.com/print201452152.html … in the August issue of Icarus there is a paper claiming some 18,000 circular mounts have been mapped on Mars in a region that might have as many as 40,000 of them. They used images from the Mars Reconnaissance Orbiter, and think they might actually be mud volcanoes. These are geological structures in which a mixture of gas, liquids and fine grained rock (mud) is forced to the surface from serveral km underground. Mud volcanoes, it is thought, are an indication of a fluid rich subsurface and life might have evolved in such an environment. That is the hope.