The 40-year archive of the Landsat satellite program is the most extensive, longest-running record of Earth observations from space. This incredibly valuable resource has yielded important discoveries, aided international efforts to better manage our environment and provided inspiration to both scientists and the public. On top of all of that, the seven Landsat satellites have returned an array of amazingly beautiful images that have allowed us to see and appreciate Earth in a new way. The flow of spectacular, continuously captured imagery will continue with Landsat 8, due to launch in 2013. To celebrate the launch of the Landsat program's first satellite, Landsat 1 (originally named Earth Resources Technology Satellite 1) on July 23, 1972, the USGS and NASA -- which jointly run the Landsat program -- have released 10 of the most significant images from the mission's history. Because one of Landsat's strengths is cataloging change on the Earth's surface over time, many of the images on the following pages are presented as time-lapse videos. Images, videos and captions courtesy of NASA and the USGS. Above: The Shrinking Aral Sea Since the 1970s, Landsat has been a witness to the changes to the Aral Sea. Scientists

studying the lake have used Landsat satellite images to go back in time to determine

the amount of water loss and the changes to the shoreline. They have also used

satellite imagery to tell its story. "If you tell somebody the Aral Sea is drying, nobody will know where the Aral Sea is,"

says Ashibindu Singh at the United Nations Environment Programme Division of Early

Warning and Assessment. "When they see the bigger picture of how many square

kilometers have dried up, then people start paying attention." Singh's group uses satellite imagery, especially time-series data, to communicate

environmental problems to the outside world. The Aral Sea is one of many lakes

worldwide whose rivers have been partially diverted for agriculture. "We see a similar

thing happening with some of the other lakes, like Lake Chad in Africa, Lake Faguibine

in Mali," says Singh. The Kazakstani government, with funding from the World Bank, completed a dam

in 2005 that separates the North Aral Sea from the large southern basin. Fed by the

remains of the Syr Darya River, the shoreline of this much-reduced lake has since

stabilized and fish are returning. Images: Above: The Aral Sea in 1998 (left) and 2010 (right) (USGS EROS Data Center). Right: The Aral Sea in 1977 (USGS EROS Data Center).

Caption: Ellen Gray, NASA's Goddard Space Flight Center.

Columbia Glacier: A Swift Retreat Our planet has more surface covered with water than land, and some of that water has been held in cold storage. Glaciers, such as the Columbia Glacier in Alaska, both record Earth's climate in their dense layers of ice and affect the climate itself when their white surfaces reflect solar radiation back into space. In this series of images from 1986 to 2011, taken with Landsats satellites 4, 5, and 7, the Columbia Glacier in Alaska’s Chugach Mountains is in decisive retreat. The false-color image shows ice in blue and vegetation in green. The dark blue that represents ocean water has opened and crept 12 miles (20 kilometers) up the mountain where the glacier used to be. The Columbia Glacier is a tidewater glacier and, as such enters the sea. These types of glaciers have retreated rapidly during the last century. The Columbia Glacier is only one point in a trend Landsat has witnessed over the past 40 years: glaciers are retreating all over the world -- a clear consequence of contemporary climate change. According to a 2009 study by the U.S. Geological Survey, 99 percent of American glaciers are shrinking. Glaciers grow by snow added in their upper part, also known as the accumulation area, and shrink by loss of ice through melting in their lower part, known as the wastage area. Glaciers tell a story of climate conditions—advancing when temperatures are cool enough to conserve glacial ice and receding when temperatures cause melting. Glaciers advance and retreat from season to season, so it takes observations over decades tell whether a glacier is generally expanding and advancing or shrinking and retreating. There once was a time when vastly more of our world was coated with ice. During the Pleistocene Ice Age, at times an estimated 30 percent of the land was ice covered, all that trapped water meant that there were lower sea levels worldwide. In places there was so little water, bridges of land opened up and created passageways for migrating humans. Today, the opposite is happening. About 10 percent of Earth's surface is covered in glaciers and ice sheets, holding less than 2 percent of our planet’s water. And glaciers are melting, releasing their water and contributing to sea level rise. With one third of the world’s 7 billion people living at or near a coastline, these rising seas could have serious consequences. Video: The Columbia Glacier in Alaska is one of many vanishing around the world. Glacier retreat is one of the most direct and understandable effects of climate change (NASA's Earth Observatory).

Image: Standing 100 feet above the bay, a tower of ice in the process of becoming an iceberg separates from Columbia Glacier's terminus (U.S. Army Engineer Research & Development Center).

Caption: Lisa-Natalie Anjozian, NASA's Goddard Space Flight Center.

Yellowstone National Park Historic Fires of 1988 Yellowstone National Park—the world’s first national park created in 1872—was transformed into an apparent wasteland during the three months of summer 1988 when it seemed that its beauty, and carefully legislated and shepherded legacy, would all go up in smoke. On June 14, 1988, just north of the park boundary, a small fire started on Storm Creek. Then, more fires started, sparked by both lightning and humans, and they multiplied and merged: Shoshone Fire, Fan Fire, Red Fire, Lava Fire, Mink Fire, Clover Fire, North Fork Fire, Hellroaring Fire, Huck Fire. Eyewitnesses described mushroom clouds roiling above the trees. The fires kept growing until they doubled in size. What weather created—historic drought that produced the conditions, which allowed fire to thrive—only weather could quell. Despite the efforts of 25,000 people fighting the fire, at a cost of $120 million—the largest fire-fighting effort in United States history up to that time—it was not until rain and snow began to fall on September 11 that the fires' rampage through the Yellowstone area was stopped. Why did these fires burn on such a massive scale? A look at the Landsat images provides a significant clue. In the first image of the sequence, from 1987 before the fires started, a very obvious vertical line can be seen near the left edge of the frame. That left edge represents a real boundary on the landscape that is the result human activities and land management policies. To the left (west) of the park boundary, land has been managed for multiple purposes, including clear-cutting of forests for timber production. To the right of the boundary, the park has been managed for preservation. The dark green represents thick forests that were protected from logging, but also, according to earlier philosophies of management that prevailed over much of the twentieth century, protected from fire. Decades of fire suppression, historic drought and a significant number of lightning strikes created the conditions that allowed the massive conflagration that, when all was said and done, burned or scorched nearly 2 million acres. Though people fear it, fire is a human disaster, not an ecological one. Fire—even one as intense and widespread as the one that burned the Yellowstone area in 1988—is a natural process. Ecosystems will, given time, recover. In the recent satellite era, Landsat images have contributed to the field of fire science, helping researchers understand fire danger, wildfire behavior, and the effects of wildfire on a landscape. Satellite data has become a tool for identifying different fuels, such as grasses, shrubs, and trees, which burn at different temperatures and are consumed by fire at different speeds, and whether they are lush or tinder dry. Knowing what is on the landscape can help managers anticipate a slow, creeping fire, a fast-racing grass fire, or an intense, crown fire that torches trees. Satellite imagery also aids scientists' understanding of how the land recovers. Able to capture reflected light characteristic of charred areas, shown in red in the time-lapse animation above, Landsat has shown scientists where grasses and saplings are growing on the burn scars of the 1988 fires. "The fires profoundly affected the ecology of the park, and still to this day, as you can see in the images, the imprint of the fire remains. The recovery is certainly going to take decades if not centuries to actually occur," says NASA Landsat project scientist Jeff Masek at Goddard Space Flight Center. Video: In 1988, fire transformed Yellowstone National Park into an apparent wasteland. Landsat captured the burn scars from the fires and watched the progress of the forest's recovery (NASA's Goddard Space Flight Center/NASA Earth Observatory).

Images: 1) A Bunsen group of firefighters putting out brush fire during the 1988 Yellowstone fires (National Park Service/Jim Peaco). 2) Bunsen Peak after the 1988 fires shows patches of surviving trees (National Park Service/Jim Peaco). 3) Taken ten years after the fires in 1998, young lodgpole pines grow in a stand of dead and burned trees (National Park Service/Jim Peaco).

Caption: Lisa-Natalie Anjozian, NASA's Goddard Space Flight Center.

International Borders: Mexico and Guatemala A glance at a traditional map shows neatly printed names and sharp lines dividing countries from one another. When the view switches to satellite imagery, human political boundaries often disappear. But sometimes the political realities of a country are written into the landscape, and never was that more clear than in this Landsat image of the Mexico-Guatemala border. Produced in 1988, the image above so starkly shows a line between forest clearing in Mexico and untouched forest in Guatemala that it became the driving force behind the establishment of 4 million acres of protected lands in Guatemala and cooperative conservation efforts across that very border. Proposed changes to a different section of the border were ultimately what led to its imaging from space. Meandering north toward the square corner, the Usumacinta River forms the diagonal section of the border between Mexico and Guatemala, in the late 1980s, a plan was developed to dam the Usumacinta River for hydroelectric power. But located in the river valley are also a number of ancient Maya cities that conservationists and archeologists wanted to see preserved. The National Geographic Society partnered with NASA in 1988 to document both these known and undiscovered archeological sites before the damming of the river. "We were trying to see as much archeological information as we could before the flood waters removed the modem day Maya Indians as well as destroyed the ancient sites," says archeologist Tom Sever, who led the project. Now at the University of Alabama, Huntsville, he worked at NASA for 27 years and pioneered the use of remote sensing for finding archeological sites. As part of that effort he put together two Landsat scenes: the western portion from Landsat 4 as seen on May 20, 1988, and the eastern part from Landsat 5 on April 14, 1986. Mexico's relative stability had led to agricultural development and clearing the forest, while Guatemala's ongoing civil war had led to rebels living in the Petén and as a side effect, limiting development and leaving the forest there untouched. "When I produced it," says Sever, "I thought everyone in the world knew about this. It was surprising to see how for everybody it was news, alarming news." "It's an amazing image," says Jim Nations, vice president of the National Parks Conservation Association's Center for Park Research. In 1988, he was a Fullbright researcher working with Guatemalan conservation groups when he joined Sever's team to ground-truth archeological sites found in satellite imagery. Says Nations, "We put the image in the hands of Andrés Lehnhoff who was the executive director of the National Council of Protected Areas of Guatemala, a friend of ours that we were working with. He has periodic meetings with the president of Guatemala, Vinicio Cerezo. He takes it in to his next meeting, a big image, like a meter across and he rolls it across his desk, and the president looks at it and says the Spanish equivalent of "son of a gun!" The border image, published in National Geographic's October 1989 issue, started a discussion of conservation between the presidents of Guatemala and Mexico that led to cooperative planning of parks in both countries. According to both Sever and Nations, at a meeting several years later President Cerezo told them both that the image of the border was the deciding factor that led to the Guatemalan Congress approving his creation 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 Nations. "That image created a 4-million acre park." The image also had a ripple effect on environmental research and conservation efforts across Central America. The image brought Sever to the attention of Jorge Cabrera, head of the Central American Commission on the Environment and Development (CCAD). "That led to an agreement between NASA and CCAD to conduct environmental types of research, and that agreement in 1992," says Sever, "eventually led to the development of the SERVIR program." SERVIR, meaning 'to serve' in Spanish, is a joint venture between NASA and the U.S. Agency for International Development that provides satellite-based Earth observations and science applications to developing nations. NASA's Marshall Space Flight Center in Huntsville, Ala. manages the program, which began in 2004. Its first local hub opened in Panama in 2005 and since then it has grown to cover developing regions all over the world. For Sever, the power of that image changed the direction of his research. Originally a desert archeologist, after his first project into the jungle he stayed to explore environmental impacts on ancient Maya societies, including deforestation. In addition to their archeological research, he and his research team continued to use Landsat to monitor the tropical forests in the Petén. Since the end of Guatemala's civil war in 1996, commercial logging, cattle ranching and agriculture have contributed to current deforestation. "It's been dramatic how quick things have changed," says Sever. As part of their verification of satellite observations in 1988, Sever and his research team rented a plane and flew along a road built into the jungle. "It looked like a sea of green out each side as we followed that road," he says. "In just the matter of a few years, the final time I took the route, you couldn't see any trees like you used to in any direction out the side." But the Maya Biosphere Reserve still exists today. Despite the encroachment, Jim Nations says, "The fact that [the Reserve is] still there is to me a sign of success because if we hadn't had that image, if we hadn't created the law, then that entire area would be mostly gone." That's the power of remote sensing, he adds. "You've got two major benefits. One of them is the analytical ability, the fact that you can actually calculate the size of areas, the amount of deforestation, the distance between two places. And then the 'wow' factor is that impact that you get when you roll an image out on your desk for the first time and you see it, you actually see it as if you were 571 miles up in space. It just blows you away." Landsat satellites have been imaging Earth since 1972, and the data they return is one of the tools used by the United Nations to monitor deforestation around the globe. Images: Top: The image on the right shows the same scenes produced in 1988 of the Mexico Guatemala border. The band combination is 5-4-3, which shows bare ground in pink, young regrowth and farms in pale green, and trees in darker green. On the left, the image shows the same area in 2011. While the border is still visible, logging and agriculture have taken down most of the trees outside, and sometimes inside, the Maya Biological Reserve (NASA's Earth Observatory). Right: The original 1988 image of the border produced by Tom Sever and shown to the leaders of Mexico and Guatemala (NASA).

Caption: Ellen Gray, NASA's Goddard Space Flight Center.

Kuwait Oil Fires In 1991, Landsat captured the devastating environmental consequences of war. As Iraqi

forces withdrew from Kuwait, they set fire to over 650 oil wells and damaged almost 75

more, which then spewed crude oil across the desert and into the Persian Gulf. Fires burned for ten months. According to a 2009 study published in Disaster

Prevention and Management, firefighting crews from ten countries, part of a response

team that comprised approximately 11,450 workers from 38 countries, used familiar

and also never-before-tested technologies to put out the fires. When the last one was

extinguished in November, about 300 lakes of oil remained, as well as a layer of soot

and oil that fell out of the sky and mixed with sand and gravel to form 'tarcrete' across 5

percent of Kuwait's landscape. Emergency responders and scientists in Kuwait used Landsat and other satellite data

to locate and monitor the plumes of smoke and burning wells. The three images above

from Landsat 5's Thermal Mapper show Kuwait in August 1990 before the fires, June

1991 while the fires were burning, and January 1992, two months after the last fires

were put out. In this 3-band composite (7-4-2), Landsat-5’s shortwave infrared band

(band 7) easily detected the flames burning at over 1300°F (700-800°C). The fires were

so hot that the detectors overloaded temporarily, turning the saturated red dots into

saturated lines visible in the June 1991 image. Subsequent studies used Landsat to look at the before and after effects of the fires and

to monitor the changes to the oil lakes over the past 22 years. The lakes are visible in

the 1992 image around the area of the former fires. An estimated one to 1.5 billion barrels of oil were released into the environment. After

most burned, 25 to 40 million barrels ended up spread across the desert and 11 million

barrels in the Persian Gulf, according to a 2012 paper published in Remote Sensing of

Environment. For comparison, the 2010 Deepwater Horizon spill into the Gulf of Mexico

is estimated to have released nearly 5 million barrels of oil. Kuwait's landscape has

recovered somewhat. Clean up efforts have removed 21 million barrels of oil from the

desert, but an estimated 1 million barrels still remain. Top Images: Kuwait oil fields in, from left to right, 1990, 1991, and 1992. (NASA's Goddard Space Flight Center). Right Images: 1) Black smoke plumes stream into the skies around Kuwait City in April 1991 five weeks after the fires were set. (NASA's Earth Observatory). 2) The oily plumes extended three to five kilometers up into

the atmosphere and hundreds of kilometers across the horizon (NASA's Earth Observatory).

Caption: Ellen Gray, NASA's Goddard Space Flight Center.

Mount St. Helens: Volcanic Eruption and Recovery Most of the geologic processes that shape our planet, such as the creeping movement of tectonic plates, are often too slow to see on human timescales, but every so often, geology produces a moment with in-your-face intensity. The explosive eruption of Mount St. Helens in Washington state on May 18, 1980, was such a moment. Situated on a subduction zone where the Juan de Fuca plate in the Pacific descends under the North American plate, Mount St. Helens is one of a number of Cascade Range volcanoes that stretch from British Columbia to northern California. The peak is the most active volcano of the group. Landsats 2, 3, 5 and 7 captured the Mount St. Helens eruption and subsequent recovery of its surrounding ecosystem over the last 32 years. The scenes collected by Landsat 2 and 3 from 1980 to 1983 show vegetation in red. Natural color images appear with the launch of the new Thermal Mapper instrument on Landsat 5 in 1984 and continued with Landsat 7. The first three seconds of the visualization (above) depict the condition of the volcano prior to the morning of May 18. It has a conical, glacier-clad peak like the others in the Cascades chain and had been inactive since the mid-nineteenth century. Scientists began actively monitoring Mount St. Helens in March 1980 when the volcano "reawakened" with a 4.2-magnitude earthquake and started venting steam. On the morning of the historic eruption, a 5.2-magnitude earthquake triggered the sequence of events that would be life-altering too many in the area. A massive slab of the northern slope of Mount St. Helens collapsed and roared over the landscape in an enormous debris avalanche -- the largest in recorded history. With a gigantic hole ripped down the volcano’s side, superheated gases and rock fragments exploded laterally instead of vertically -- something that had not been witnessed and recorded before in modern times. The blast raged with wind speeds reaching 200 to 250 miles per hour (320 to 400 kilometers per hour) at temperatures of 680˚F (360˚C), flattening and scorching trees. For more than 9 hours after the lateral blast, Mount St. Helens gushed an ash plume that reached 15 miles high into the atmosphere, and in 15 days, circled the globe. Deadly pyroclastic flows, at least 1,300˚F (704˚C), spewed from the crater and covered 6 square miles (15 square kilometers) under feet of choking pumice. The summit and northern slope were obliterated. The surrounding forest ecosystem was wiped out: Trees were burned, flattened or simply gone. Churning mudflows poured down the Toutle River, which was filled with trees, mud and boulders. When the roiling flow reached the Columbia River, it blocked the shipping channel. In the visualization, the two squiggly lines that grow fat on the left side were the two forks of the Toutle River choked with debris. Fifty-seven people died in the immediate aftermath of the eruption, including David Johnston, the U.S. Geological Survey geologist who had been monitoring the volcano from the ridge that now bears his name. After the eruption, Mount St. Helens delivered another surprise. Scientists expected life to return in predictable ways, following well-known stages in ecological succession. They thought that in some areas nothing living could have survived. But that’s not how things happened. For example, the time of day of the eruption and the season of the year meant some nocturnal animals were protected in burrows. Others had not yet arrived from migration. Dormant plants below ground also were protected. Rocky outcroppings, cliffs and snow patches sheltered some animals and plants. Colonization and biological interaction in the blast area of the post-eruption landscape of Mount St. Helens created unique opportunities to learn how plants and animals respond to a massive, infrequent disturbances, which in turn has enabled scientists to understand and inform management plans for other disturbed areas. With its record of changes on the landscape year after year, scientists have used Landsat images to accurately characterize the pattern of ecosystem recovery after natural disasters. Video: NASA's Goddard Space Flight Center/NASA Earth Observatory

Caption: Lisa-Natalie Anjozian, NASA's Goddard Space Flight Center.

Uncovering Antarctica The first ever high-resolution, three-dimensional true color map of Antarctica is the result of more than 1,100 Landsat 7 images stitched together to create the Landsat Image Mosaic of Antarctica (LIMA), released in 2007. "This is something that would have been impossible without Landsat," says Thomas Loveland, a scientist with the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center in Sioux Falls, S.D. "LIMA was the first comprehensive and high-resolution view of one of the most remote regions on Earth," he adds. NASA worked with the USGS, the National Science Foundation and the British Antarctic Survey to create the LIMA map. It and all the individual scenes that make up the map, which cover every bit of Antarctica, are available on the Internet, free of charge by the USGS, providing everyone in the world a view of the highest, driest, coldest, windiest and brightest of all of the Earth's seven continents. To create the LIMA map, scientific visualizers combined Landsat 7 satellite imagery acquired in 1999 and 2001 and a digital elevation model with field data measurements. This bird's eye view of Antarctica led to a surprising discovery about one iconic cold-weather bird, the Emperor penguin. "We were able to find entirely new colonies of Emperor penguins by looking at the Antarctica coastline from space," says Peter Fretwell, a geographic information scientist at the British Antarctic Survey. "It was a serendipitous discovery," Fretwell says. "If this data wasn't free, we would have never been able to do our research." Fretwell and his colleagues were downloading and viewing hundreds of LIMA scenes to map a section of the Antarctic coastline when Fretwell noticed an unusual feature. "I could see brown stains in the LIMA imagery," he says. Those brown stains are where colonies of Emperor penguins were breeding. "We started going around the whole of the coastline, using about 200 scenes, looking for these dark areas," Fretwell says. By measuring these stains, Fretwell and his colleagues ultimately discovered 10 completely new colonies and pinpointed the location of six previously known ones, ultimately mapping the location of 38 Emperor penguin colonies across the entire continent. The discovery was only possible using satellite data, he says, because for the Emperor penguin, those colonies are only their temporary home. "Emperor penguins breed in Antarctica almost exclusively on sea ice," Fretwell says. Come summer, the ice melts away, so researchers previously to find penguins would have to brave bracingly cold early-spring temperatures and travel to ridiculously remote locations, and even then they couldn't be sure they'd found every colony. Researchers have also used LIMA to track Antarctica's mighty glaciers. Landsat captured the telltale 'flow stripes' of these slow-moving rivers of ice as they creep, ever so slowly, across the continent. Much of the ice in Antarctica is trapped within these glaciers. They form when snow, accumulating for tens to hundreds of years, eventually succumbs to gravity, and compressing enough to form dense, glacial ice. Underneath these moving bodies of ice are mountains, plains and ocean basins that are almost completely concealed by ice. LIMA's true-color imaging also showcases one of Antarctica's most fascinating features -- blue ice. These ice crystals are larger than average snow crystals, making their absorption of red light, and reflection of blue light, more obvious. LIMA also shows quite clearly the Pine Island Glacier, a massive river of ice that's 190 miles wide and 30 miles long (~306 kilometers wide, ~48 kilometers long). In October 2011, NASA's Operation Ice Bridge mission discovered a massive crack stretching across the glacier. It's about 820 feet (~250 meters) across at its widest point and about 200 feet (61 meters) at its deepest. If the glacier breaks at this crack, it will create a massive iceberg of 350 square miles (907 kilometers), about the size of all of New York City. In addition to this huge crack, one that's deep enough to nearly swallow the entire Statue of Liberty, continuous measurements by Landsat, other satellites and field stations show that the entire Pine Island glacier is rapidly shrinking. Scientists believe that warm water is undercutting the glacier, melting it from below and thinning the ice. Scientists continue to track Antarctica's ice and wildlife using Landsat 7, which remains in operation 13 years after its launch. The next satellite in the Landsat series, which began in 1972 with Landsat 1, is scheduled to launch in February 2013 from Vandenberg Air Force Base in Lompoc, Calif. Known as the Landsat Data Continuity Mission (LDCM), it will extend the world's longest-running satellite program for global land observations into the future. Video: In 2007, more than 1100 Landsat 7 images were used to create the first ever, high-resolution, true color map of Antarctica. The Landsat Image Mosaic of Antarctica is a virtually cloud-free, 3-D view of Antarctica's frozen landscape (NASA's Goddard Space Flight Center).

Images: 1) NASA's Operation IceBridge discovered this massive crack across the Pine Island Glacier. It is deep and wide enough to nearly engulf the Statue of Liberty, being 820 feet (~250 meters) across at its widest point and about 200 feet (~61 meters) at its deepest (NASA's Operation IceBridge). 2) NASA's Michael Studinger aboard the IceBridge DC-8 plane that surveyed the glacier. The area cracking off could become an iceberg the size of all of New York City, about 310 square miles (800 sq. km) (NASA's Operation IceBridge).

Caption: Aries Keck, NASA's Goddard Space Flight Center.

Beijing: The Rise of an Economic Superpower Beijing is one of the oldest, and now, one of the most densely populated cities in the world. In this animation of Landsat images from 1972 to 2010, the explosive growth of this ancient city is clearly visible. In 1972, Beijing's population was about 7.9 million people. By 2010 the population swelled to more than 12 million. The success of economic reforms beginning in the 1970s fueled the dramatic growth. The 30-meter resolution of Landsat scenes is ideal for portraying a view of this and other cities as they grow and change. Landsat's 40-year-long record can be used like a time machine, allowing viewers to jump back years or even decades to compare one period of a city's life to another. "In these views of Beijing, Landsat tracks not only an impressive example of global urban growth, but also the footprints of social and political change," says Tom Loveland, a scientist with the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center in Sioux Falls, S.D. In the late 1970s, the Chinese communist leadership began to embrace market-oriented economic reform. The ensuing economic boom caused the city to expand rapidly. In the 1980s, a series of 'ring roads' were added that encircle the city. This economic openness led some to agitate for political reforms and in 1989 there were mass demonstrations in the city's center at Tiananmen Square near the Forbidden City area. In the 1990s, the Chinese government gradually opened up its political system to continuing economic reforms. These efforts were rewarded internationally in 2001 when the International Olympic Committee chose Beijing as the host for the 2008 Summer Olympics. China's economic reforms have resulted in a vast and sudden expansion of Beijing. Today a total of six ring roads loop around the city center, separating regions of the city by specialties, like flourishing shopping areas, a financial district and a major electronics center. To the west and northwest of the city runs the rugged Taihang Mountains, and so the city's spread is more vigorous to the south and east across the relatively flat coastal plain. This expansion stands in strict contrast to the Beijing of the 1970s and before. Up until 1979, the government restricted housing in the city, limiting it to the confines of the "Outer City." Previously a walled fortress, its outline is still visible today due to the creation of canals and roads along the path of the original wall. Inside this rectangular boundary is the ancient heart of the capital, the moat-lined Forbidden City. This is where the Imperial Palace still stands, once home to 500 years of Chinese emperors. Beijing was established as a city in 1045 B.C. King Wu was the first to declare the city as a capital in 1057 B.C. It was Kublai Khan who established the Forbidden City in 1260 A.D. It still stands as Beijing's city center. In 1421 the Chinese took the city back and gave it its current name of Beijing. Having served as the capital of the Liao, Jin, Yuan, Ming and Qing Dynasties, this modern metropolis is now the capital of the People's Republic of China. Video: The Chinese capital of Beijing as seen by Landsat 3 in 1978 and Landsat 5 in 2010. In 1978, the image was acquired by Landsat 3's Multispectral Scanner System instrument on June 21, capturing the green, red and near-infrared bands. These same bands are visible in the 2010 image, captured on August 8 by the Thematic Mapper instrument aboard Landsat 5 (NASA/Goddard Space Flight Center Scientific Visualization Studio).

Caption: Aries Keck, NASA's Goddard Space Flight Center.

Mining for Water in the Kansas Heartland Garden City, Kansas is at the heart of the American breadbasket where farmers grow corn, wheat and sorghum and raise cattle. Over the last sixty years, two technologies have transformed production from rain fed-oriented agriculture to high-intensity irrigated agriculture, a change that transformed the local economy. Instead of relying on the rain, Garden City farmers now use low-cost groundwater pumps and a technique called "center-pivot irrigation" to essentially mine for water locked deep underground. Garden City's current bounty is possible because beneath these farmer's fields is a vast reservoir of water, called the Ogallala Aquifer. This vast stretch of groundwater touches eight states, from South Dakota and Wyoming to New Mexico and Texas and so, because the semi-arid climate of the High Plains doesn't receive enough rainfall to support intensive agriculture, farmers pump this trapped water above ground to irrigate their fields. The growth and change in irrigation practices is visible in these three Landsat images from 1972 (bands 6-5-4 from Landsat 1), 1988 and 2011 (bands 4-3-2 from Landsat 5). In these comparable band combinations, healthy vegetation appears bright red while sparse grasslands and fallow fields are in shades of green. Located in the southwest part of the state, over time Garden City's rectangular fields of rain-fed farms and more traditional irrigation methods gave way to the large circles made by center-pivot irrigation. Farmers pump water directly from groundwater wells in the center of the field to a long pipe studded with low-hanging sprinklers. The pipe rotates from the center like the hand of a clock, watering the fields. It's a labor and water-saving method that has revolutionized agriculture worldwide, increasing yields and allowing food production in areas where plants would otherwise wither from drought. Because the Ogallala aquifer recharges from new rainwater slowly, some of the water used to irrigate these fields is actually water that's been trapped underground since the last Ice Age. Even with the rise of water-conserving center-pivot irrigation and other efforts to conserve, this aquifer is slowly going dry. According to the U.S. Geological Survey data from 1980-1995, water levels in southern sections of the Ogallala Aquifer during that time dropped 20 to more than 40 feet (6 to 12 meters). And the Kansas and Texas droughts in 2011 and 2012 have dropped water levels by several more feet. The U.S. Department of Agriculture uses Landsat data to monitor crop inventories across the U.S. and the globe. The images are also used to evaluate insurance claims and prevent fraud. False-color images like these show healthy crops as bright red, making them easy to distinguish and measure. In the last ten years scientists have also developed a method of detecting water using the thermal infrared bands on Landsats 5 and 7. These are sensitive to temperature. After a plant has absorbed water through its roots and used it, the plant 'breathes' out excess water vapor through its leaves. Called transpiration, this process, as well as the evaporation of water from wet soil, together ultimately lowers the overall temperature of the area. Using a set of equations, researchers used Landsat observations in the thermal infrared to create an estimate of water usage that water managers use to administer their resources. This method is quite often used in Idaho and Nevada where water is a scarce resource. Images: Top: These images from 1972, 1988 and 2011 show the transformation of Kansas farmland from dry land, rectangular fields to circular irrigated fields from center-pivot irrigation systems. The mining of ground water for agriculture has been a significant trend globally over the last half-century, and these images of a region in Kansas highlight the trend within the United States (NASA's Goddard Space Flight Center). Right: Nine-mile-wide strips of the broader Garden City area in 1972, 1988 and 2011 (NASA's Goddard Space Flight Center). (

Caption: Ellen Gray, NASA's Goddard Space Flight Center.