From the sun, we head a little closer to home to the other heavenly body that most impacts our planet -- the moon.
This app allows you to make like an astronaut without ever leaving the ground. You can view the moon either as it appears from your location on Earth, or with a simple click, turn it into a sphere that lets you spin it to explore every nook and crater. Touching its surface brings up informational terrain tags.
With another click, the tags vanish and in their place appear links to the various spacecraft that have landed on the moon. Two-fingered swipes turn the moon, one-fingered swipes move the moon on the screen and the standard pinch motion zooms you right down onto the surface with astoundingly clear rendering that earns this app its HD title. In full zoom, it feels just like you're gliding over the stark landscape.
The night vision features turn the screen an eye-friendly red. There is also a compass overlay function. One of the most fun features of the app is that while you spin the moon, the Earth and sun appear in their correct positions in the distant sky. You have the perspective of being on the moon.