Today's Image of Mars is of the volcano Tharsis Tholis, as taken by Mars Express Orbiter's High Resolution Stereo Camera (HRSC). The volcano rises 8km above the surrounding terrain and is one of the many Tharsis Volcanoes. It stretches 155 x 125km at its base and its caldera (opening) is 32 x 34km.
Tharsis Tholis is unique among Martian volcanoes due to the degree by which it has been modified by faulting. Large faults cut across the entire volcano. dividing it into several major sections. [View images of Tharsis Tholis as taken by other cameras aboard Mars Express]
Click on the image below to see the original high resolution image from Mars Express.