Swiss Cheese Like Landscape on Mars

Why do parts of the south pole of Mars look like swiss cheese ? This little-understood landscape features flat-topped mesas nearly 4 meters high and circular indentations over 100 meters across. Since this swiss-cheese topography is unique to the polar cap covering southern Mars , exogeologists speculate that mesa composition might be high in frozen carbon dioxide ( dry ice ). Additionally, dry ice might have had a role in this strange landscape 's creation. In the above picture , the Martian surface is illuminated by sunlight from the upper right. The above picture was taken in August 1999 by the robot Mars Global Surveyor spacecraft currently orbiting Mars .