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.
You can manipulate time with Mars Globe HD. You can see Mars at the current time, or you can manipulate the position of Mars to the Sun so that you can control the shadows and bring surface objects into dramatic relief.
This is a big app; it's almost 600 MB to download, so make sure your iPad has the room. My science classes were never like this. I can't imagine a better way to spend US$0.99, and it makes a terrific demo of the power of the iPad to inform and entertain.
An HD version of the free Moon Globe app that I've reviewed before will be out soon.
I pulled some screenshots so that you can see Mars Globe HD doing its stuff. These previews, however, don't compare to seeing this app in action on the iPad screen.