This photo was taken on September 17, 2008, when Mars Express' orbit was positioned so that its apoapsis -- its farthest reach from Mars -- was over the high latitudes of the southern hemisphere.
It was also midwinter in the southern hemisphere. So you see seasonal frost surrounding the south pole; the polar cap is in winter darkness. The frost is especially bright within Argyre planitia -- an ancient impact basin -- and the smaller, circular crater Galle the lower right of Argyre. (If you squint, you can just make out some of the features within Galle that make it look like a happy face.) To the north, you can just make out the outline of Valles Marineris and Candor Chasma, the smaller canyon to the north of and parallel to the main canyon. Most of the disk that we see is Noachis Terra, some of the most ancient terrain on Mars. To the north, high cloud hazes the view.