Strange Polygons on Mars

Hexagon with Square in Center in Honeycomb Terrain, Cydonia Region, Mars

The new Mars, Cydonia photo from MSSS has several large areas honeycombed with polygonal forms, predominately hexagonal. This kind of texture is typical of basalt flows on Earth. On earth the polygons are thought to be caused by differential cooling between the interior of the polygon and the sides forming hexagonal convection cells. The cell edges fracture as the basalt cools. This "columnar jointing" is very common in basalts and often forms hexagonal columns meters wide and sometimes 30 meters high. Devil's tower in Wyoming and "Giant's Causeway" in Ireland are well known examples of this type of basalt formation. The polygons exhibited here are much, much bigger in scale, but it seems likely that a similar process must have been involved. The large hexagon with the square in the middle seems out of place here. All the other polygons appear dark and low in the center, whereas this one has a large nearly square column in the center. My feeling is this is a natural formation, although very unusual. What might have caused one convection cell to be so different than all the ones surrounding it? Could it be artificial? We will never know until someone walks there and studies it.