A joint venture between NASA and the U.S. Geological Survey, the Landsat program is the longest running enterprise for acquisition of satellite imagery of Earth providing images of the planet for the last 40 years. The Landsat satellites make loops around the earth constantly collecting images of the surface through the use of a variety of sensing devices. Since the beginning of the Landsat program in 1972, the images and data have been available to all countries around the world, and used in a variety of research work such as measurement of rain forest loss, determining urban growth, and population change.
Beyond the scientific information they supply, some Landsat images are simply striking to look at, presenting spectacular views of mountains, valleys, and islands as well as forests, grasslands, and agricultural patterns. By selecting certain features and coloring them from a digital palate, the U.S. Geological Survey has created a series of "Earth as Art" perspectives that demonstrate an artistic resonance in satellite land imagery and provide a special avenue of insight about the geography of each scene.
To mark the 40th anniversary of the Landsat mission, the public was asked to vote for the best images out of more than 120 taken by the Landsat satellites over the years. The top five selections, based on more than 14,000 votes, are featured here.
1. In the style of Van Gogh's painting "Starry Night," massive congregations of greenish phytoplankton swirl in the dark water around Gotland, a Swedish island in the Baltic Sea. Population explosions, or blooms, of phytoplankton, like the one shown here, occur when deep currents bring nutrients up to sunlit surface waters, fueling the growth and reproduction of these tiny plants.
2. Countless lakes, sloughs, and ponds are scattered throughout this scene of the Yukon Delta in southwest Alaska. One of the largest river deltas in the world, and protected as part of the Yukon Delta National Wildlife Refuge, the river's sinuous waterways seem like blood vessels branching out to enclose an organ.
3. Small, blocky shapes of towns, fields, and pastures surround the graceful swirls and whorls of the Mississippi River, the largest river system in North America. Countless oxbow lakes and cutoffs accompany the meandering river south of Memphis, Tennessee, on the border between Arkansas and Mississippi.
4. What look like pale yellow paint streaks slashing through a mosaic of mottled colors are ridges of wind-blown sand that make up Erg Iguidi, an area of ever-shifting sand dunes extending from Algeria into Mauritania in northwestern Africa. Erg Iguidi is one of several Saharan ergs, or sand seas, where individual dunes often surpass 500 meters (nearly a third of a mile) in both width and height.
5. The scary face in this image is actually inundated patches of shallow Lake Eyre (pronounced "air") in the desert country of northern South Australia. An ephemeral feature of this flat, parched landscape, Lake Eyre is Australia's largest lake when it's full. However in the last 150 years, it has filled completely only three times.