You've seen all manner of amazing space photos from NASA, but some of the space agency's most extraordinary images are actually of Earth itself. The NASA Earth as Art app (free) celebrates the beauty of our home world, as seen from a perspective only achievable from space. Although each image is captioned with detailed descriptive text, the real focus is the sheer beauty of the landscapes, many of which may look unearthly but are as terrestrial as they come.

A Bird's-Eye View of Earth
The images themselves are beautiful and amazing. They come from five Earth-orbiting satellites: Terra, Landsat 5, Landsat 7, EO-1, and Aqua. These satellites can measure light in wavelengths beyond the visible range, so in many cases the images may reveal more than what meets the eye, appearing in enhanced color, also know as false color. For those curious about the satellites, the app also contains links to the NASA mission pages for each of these eyes in the sky.

View All 8 Photos in Gallery

These richly varied images encompass a huge range of geological features: deserts, dune fields, oases, outcroppings, lakes, rivers, deltas and alluvial fans, volcanoes, mountain ranges, islands, and more. One section is for atmospheric images, showing unusual cloudscapes from above. Only a few images show signs of human activity, including one shot of Peru's mysterious Nazca lines and another of checkerboard farmlands around the Mississippi River. Without exception, the images are visually striking. The thorough captions help viewers understand the nature of the geographic features, although they're not necessary to appreciate the photos.

Although a few of the locations may be identifiable, many are unrecognizable, appearing as exotic textures in enhanced colors. Many of them look more like abstract paintings than terrestrial landscapes. This is particularly true of some of the desert images, as well as Earth as Art is an appropriate name for the app, which is as much about aesthetics as it is about science.

Exploring the Image Gallery
The content can be explored in several different ways. On opening the app, after viewing a brief animation of images, credits, and an introduction (which you can skip), you see a grid of images with a few descriptions such as Introduction, Cover, Landsat 7, Mt. St. Helens, and so on. Descriptions (other than text accompanying the opening animation and introduction) require an Internet connection. The images and their captions, however, are accessible whether or not you're online.

Images are arranged by continent or region, starting with Africa. You move through the images using forward and back arrows. Each image has an information tab, which calls up a caption. You can tap on a tab with large thumbnails to return to the aforementioned grid, or on a tab with small thumbnails to go to the Interactive Directory, which lists all the images, by continent and location, as well as by the satellite that took them.

From the Interactive Directory, if you're online, you can also access World of Change, three time-lapse animations from NASA's Earth Observatory site showing the receding of Alaska's Columbia Glacier; geological changes at Mt. St. Helens since its eruption, and urban growth and the creation of artificial islands in Dubai. Additional content from the Earth Observatory site is also accessible through links.

One thing NASA Earth as Art lacks is any social media integration. Of course, you can always save a screenshot in your iPad and email or tweet it, or post it on Facebook, but it would be nice if there was some sort of functionality built in. It would be nice, for example, to be able to post a picture to Facebook or Twitter; the link might conceivably lead to the same image on NASA's site.

Unlike the Editors' Choice NASA App HD, which is a portal to a wide range of content, NASA Earth as Art is finely focused, comprised of aesthetically beautiful satellite photos of Earth's varied terrain. At that, it succeeds admirably. This free app is worth installing by any iPad owner interested in geography, photography, or art.