During its 40 years in space, the Landsat program has provided scientists with a clear and sometimes terrifying picture of our changing planet.
Stan Freden, Landsat's project scientist in its early years, with a model of Landsat 1 (NASA)
Today marks the 40th anniversary launch of the first of the Landsat satellites. In the four decades since, six more satellites have taken to the Earth's orbit (the next is planned for early next year), and they have captured what is the longest, uninterrupted data set on the Earth as viewed from Space. Scientists use Landsat data to monitor changes in the Earth's climate, topography, geography, and biosphere. To commemorate these four decades, NASA has teamed up with the U.S. Geological Survey and selected what they consider the 10 most significant images (some a series, presented for you in video or slideshow formats) to come out of the mission thus far. Here they are in all their sometimes-beautiful, sometimes-terrifying, glory.
1. The Eruption of Mount St. Helens
In the visualization above, data from Landsat satellites show the area as it was pre-eruption (the first three seconds), following the calamity on May 18, 1981, and then the three decades of gradual recovery since. Landsats 2 and 3, which collected data from 1980 to 1983 show vegetation in red. Beginning in 1984 with the Thermal Mapper instrument on Landsat 5, the images appear in true color.
2. The Rise of Beijing
In the period from 1972 to 2010, the population of Beijing exploded, growing from about 7.9 million people to more than 12 million. Human settlement and migration on that scale can be seen from space, and Landsat was there to capture it.
3. Massive Deforestation in the Amazon
In 1993, biologists Compton Tucker and David Skole published research based on Landsat data showing that even though the rate of deforestation was lower than had been previously thought, the method by which it was occurring was worse for biodiversity than had been anticipated. That method, known as the fishbone pattern and clearly visible in the images above, works by clearing strips off of a branching pattern of roads. Though the area is not clear cut all at once (though, by the end, it is), the method greatly expands the amount of forest on an "edge," leaving it vulnerable to wind, desiccation, poachers, and other human interference.
4. The Shrinking Aral Sea
The Aral Sea used to be the fourth largest lake in the world. Today, it is just 25 percent its original size, and holds 10 percent the amount of water, and has split in two, the result of 1960s-era Soviet decisions to divert two major rivers, the Syr Darya and the Amu Darya, to irrigation of nearby agriculture. The above images, taken in 1977, 1998, and 2010, show the lake as it slowly dies. Below, a picture from Reuters showing the change as it appears from the ground.
Kazakh villagers collect metal parts of ruined ships lying in sand that once formed the bed of the Aral Sea near the village of Zhalanash (Reuters)
5. The Oil Fires of Kuwait
Over the past four decades, Landsat has captured changes to the environment, and some of those changes come not from economic growth or shifting patterns of migration, but from war. Following the Gulf War in 1991, Iraqi troops set fire to 650 oil wells as they withdrew to Iraq (the yellow line depicts the Iraq-Kuwait border). Oil from the burning well flowed across the desert and into the Persian Gulf. The fires burned for 10 months. Landsat satellites captured before, during, and after images of the crisis. Approximately 1.5 billion barrels of oil were dumped into the environment. In contrast, the 2010 Deepwater Horizon spill in the gulf let loose some five million barrels.
6. The Mexican-Guatemalan Border
In 1988, archaeologist Tom Sever put together the first of the two above images with data from Landsat. In the image, you can clearly see the dramatic deforestation in Mexico, and the relatively well-preserved forests in Guatemala, the result of a terrible civil war which had inhibited economic growth and, therefore, resource extraction. That image, published in National Geographic in 1989, jump-started a conversation about the protection Guatemala's forests would need in an era of relative peace if they were to avoid Mexico's fate. That led to the creation of the Maya Biosphere Reserve in 1990. "It's a huge protected area. It's got five national parks inside it and two or three wildlife reserves and then the rest of it is a sustainable use forest," says Jim Nations, the vice president of the National Parks Conservation Association's Center for Park Research. "That image created a 4-million acre park." In the second image above, you can see the results of the preservation efforts, in an image made from Landsat data collected in 2009 and 2011.
7. The Retreat of the Columbia Glacier
From a recent Picture of the Day (slightly edited here for clarity):
When British explorers explored Alaska's Prince William Sound in 1794, the Columbia Glacier reach down from the Chugach Mountains southward until it reached Heather Island. That's how the glacier remained until 1980, when it began rapidly retreating up the valley. Above is a false-color picture NASA's Thematic Mapper on the Landsat 5 satellite captured of the glacier in 2011. For comparison, slide to the next image, taken by the same instrument in 1986. In the pictures, snow and ice appear in blue, vegetation is green, the ocean is dark blue, clouds are white or light orange, bedrock is brown, and rocky detritus is gray. The great increase in bedrock between 1986 and 2011 is the clearest indication of the dramatic change that has taken place. The 2011 image was taken in May and thus has more snow than the 1986 image which was captured in July. Over the past decades, the glacier has retreated more than 12 miles and thinned out, losing about half of its total thickness and volume, according to NASA.
8. The 1988 Yellowstone Fire
Over the summer of 1988, fires in Yellowstone National Park burned more than a million acres of forest land, more than a third of the park. Landsat satellites captured the destruction and slow recovery, as shown in the video above. Below, an elk in a recently burned area of the park.
Wikimedia Commons
9. The Transformation of Agriculture
Three Landsat images of America's breadbasket (Garden City, Kansas, specifically) show the rise of center-pivot irrigation technology, which farmers use to tap water in the underground Ogallala Aquifer, a massive lake running under eight states, from South Dakota and Wyoming to New Mexico and Texas. In the above images, the rise of the new technology, which uses a long pipe rotating from a field's center, is visible as fields transform from rectangles to circles.
10. Mapping Antarctica
In 2007, using Landsat data, scientists released the first high-resolution, three-dimensional true color map of Antarctica, stitched together from more than 1,100 Landsat 7 images. Known as the Landsat Image Mosaic of Antarctica or LIMA, the map and more recent Antarctica observations are helping scientists track how this remote region is affected by the changes in the global climate. Additionally, in the course of their research, scientists noticed some "brown stains" in the ice, which turned out to be colonies of Emperor penguins. Ultimately they were able to map 36 penguin colonies across the continent.
Wikimedia Commons
We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.
