The images are uncannily realistic. While this app is available for the iPhone for free, the added detail and expanse of the iPad screen make this version a very different experience. You can circle Mars from any orbit that you create or take a guided tour with over 1500 surface features mapped and annotated. You can learn about the geologic features of the planet, the spacecrafts that have visited Mars, and switch the map to elevation view to get an idea of just how high some of those Martian mountains are.
If you have some 3D anaglyphic glasses around, the app will render Mars in a stunning perspective view, with the labels floating over the landscape.