This proposed future Mars landing site in Acidalia Planitia targets densely occurring mounds thought to be mud volcanoes.

Mud volcanoes are geological structures formed when a mixture of gas, liquid and fine-grained rock (or mud) is forced to the surface from several meters to kilometers underground. Scientists are targeting these mud volcanoes because the sediments, brought from depth, could contain organic materials that might provide evidence for possible past and present microbial life on Mars.
Written by: Sharon Wilson   (1 December 2010)

This is a stereo pair with ESP_025203_2250 .

More info and image formats at http://hirise.lpl.arizona.edu/ESP_019612_2250

Image: NASA/JPL/University of Arizona