1. The Many Colors of Electric Lights

    As anyone who has stood in a hardware store knows, light bulbs come in a wide range of types and colors. Incandescent bulbs have a warm glow similar to sunlight, while more energy efficient gas-discharge bulbs come in a variety of shades.

    Some of the differences in artificial lighting are visible in photographs taken by astronauts aboard the International Space Station. For instance, several distinct colors of electric light are visible in this image of the Tsushima Strait, the shallow body of water that separates southern Japan and South Korea. A member of the Expedition 37 crew took this photograph on October 11, 2013.

    A cluster of fishing boats is the source of the bluish light near the center of the image. The fisherman are likely luringTodarodes pacificus—a species known as the Japanese flying squid—to the surface with bright xenon bulbs. The city lights on the Korean side of the strait tend to have an orange glow, while those on the Japanese side are greener. The difference is related to the distribution of mercury vapor, metal halide, and high-pressure sodium lamps—the bulb types most often used for street and outdoor lightning. Mercury vapor lights tend to be green, high-pressure sodium is orange, and metal-halide lamps are bright white.

    Astronaut photograph ISS037-E-12066 was acquired on October 11, 2013, with a Nikon D3S digital camera using a 50 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by the Expedition 37 crew. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by Adam Voiland.

    Instrument(s): ISS - Digital Camera
     
  2. Kaziranga National Park, India

    In the state of Assam, in the northeastern corner of India, Kaziranga National Park protects a few hundred square miles of the Brahmaputra River’s natural floodplain. In the fertile soil washed down from the Himalaya Mountains during the yearly floods, lush grasses grow up to 20 feet high, making the park a paradise for grazing animals and their predators.

    This natural-color image from the Landsat satellite shows Kaziranga National Park on February 5, 2000. The river flows west through braided channels interspersed with sandy islands. The grassy expanse of the park to the south is dotted with pools of water.

    The hilly terrain on both sides of the river plays an important role in making the park a wildlife haven. When snowmelt and summer monsoon rains flood the lowlands, the residents—which include endangered rhinos, elephants, wild water buffalos, and tigers—migrate from the river corridor to higher ground. Small reserves and sanctuaries protect some of the forested hills south of Kaziranga, but villages and fields are mixed among them, which means that human-wildlife conflicts are inevitable.

    • References

    • Chadwick, D. (2010, August). India’s Grassland Kingdom. National Geographic, 218(2), 98-117.

    NASA image by Robert Simmon, based on Landsat-7 data from the USGS Global Visualization Viewer, and theWorld Database on Protected Areas. Caption by Rebecca Lindsey.

    Instrument(s): Landsat 7 - ETM+
     
  3. Big Bend National Park

    Alternately known as a geologist’s paradise and a geologist’s nightmare, Big Bend National Park in southwestern Texas offers a multitude of rock formations. Sparse vegetation makes finding and observing the rocks easy, but they document a complicated geologic history extending back 500 million years.

    On May 10, 2002, the Enhanced Thematic Mapper Plus on NASA’s Landsat 7 satellite captured this natural-color image of Big Bend National Park. A black line delineates the park perimeter. The arid landscape appears in muted earth tones, some of the darkest hues associated with volcanic structures, especially the Rosillos and Chisos Mountains. Despite its bone-dry appearance, Big Bend National Park is home to some 1,200 plant species, and hosts more kinds of cacti, birds, and bats than any other U.S. national park.

    Decades of research have enabled geologists to piece together Big Bend’s complex history. Between roughly 500 and 200 million years ago, when today’s North America was part of a completely different continent, a deep ocean trough extended into the Big Bend region. Sediments washed into the trough from higher ground and over time, those sediments hardened into shale and sandstone beds. Around 300 million years ago, a landmass collision to the south formed the ancestral Ouachita Mountains—some roots of which persist today in 500 million-year-old rocks near Persimmon Gap—and uplifted the area. One hundred sixty million years of erosion followed.

    About 135 million years ago, the area’s elevation was low enough to allow the intrusion of a warm, shallow Cretaceous Sea. Limey mud deposited by the sea later solidified into limestone, which appears throughout the park, including the walls of Boquillas Canyon. The shallow sea began to withdraw in the direction of the Gulf of Mexico 100 million years ago. Just as limey mud left remains, so did the sandy shores of the sea, lingering as sandstone and clay sediments around the Chisos Mountains. As the Cretaceous Period drew to a close, a new mountain chain began to rise: the Rocky Mountains. Today these mountains reach their southernmost point at Mariscal Mountain.

    Around 42 million years ago, an extremely active period of volcanism began in the region. The Chisos Mountains include the remains of ancient lava flows and ash emissions, but volcanism doesn’t always produce ash clouds and lava flows. Sometimes the rock, or magma, just pushes up through overlying rock layers without quite reaching the surface. That tough, persistent rock can then be exposed by later erosion. The Rosillos Mountains are a mushroom-shaped intrusion of such volcanic rock.

    Throughout its history, Big Bend has provided a home to animal species as varied as its shifting habitats. Fossils at Big Bend include oysters, snails, giant clams, ammonites, turtles, rhinos, rodents, pint-sized horses, dainty camels, and a nearly 50-foot-long crocodile. One of the most spectacular fossils is the largest flying animal yet discovered: Quetzalcoatlus northropi. With a wingspan rivaling that of a small airplane, the giant bird probably weighed no more than a modern adult human.

    1. References

    2. U.S. National Park Service. (2010, July 12). Big Bend National Park. Accessed July 16, 2010.
    3. U.S. Geological Survey. (2002, June 14). America’s Volcanic Past: Big Bend National Park, Texas. Accessed July 16, 2010.

    NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using Landsat data provided by theUnited States Geological Survey. Caption by Michon Scott.

    Instrument(s): Landsat 7 - ETM+
     
  4. Wyperfeld National Park

    About 25 million years ago, much of what is now the northwest corner of Victoria, Australia, sat at the bottom of a shallow sea. As the waters receded, the area changed to a near-forest of shrubs and small trees. Starting in the 1840s, after Europeans settled the region, much of the area was burned to clear land for agriculture. Wanting to preserve natural areas, naturalists began petitioning the Australian government to protect the habitat in the early twentieth century. In 1921, Wyperfeld National Park was established. In the years that followed, the park’s area expanded.

    The Enhanced Thematic Mapper Plus on NASA’s Landsat 7 satellite captured this image of part of Wyperfeld National Park on October 1, 1999, in the middle of Australia’s spring growing season. The drought-tolerant, natural vegetation of the park is gray-brown, and it contrasts markedly with the tan and green rectangles of surrounding farmland. Within the park, fires have left prominent burn scars. In this image, more recent burn scars look like off-white sand. The largest scar appears along the left edge of the image. Next to it is an older, darker scar, where vegetation has begun to recover. Another recent, sizable scar appears northwest of Lake Hindmarsh.

    This semi-arid region is watered by the occasional overflowing of the Wimmera River, which supplies Lake Hindmarsh and Lake Albacutya. Occasional rains also bring to life dormant, diminutive desert plants. Characteristic of Australia, however, the natural vegetation preserved within the park boundaries appears less lush than that of the surrounding, irrigated farmland. The apparent dullness is probably due to various traits that plants living in such an arid location have evolved, including thick bark, and sparse, small leaves or needles. For example, the eastern part of the park is covered by mostly by different species of mallee, shrubby Eucalyptusspecies. The leaves of Eucalyptus plants often have a gray-green cast.

    NASA image created by Jesse Allen, using Landsat data provided by the United States Geological Survey. Caption by Michon Scott.

     
  5. Petrified Forest National Park, Arizona

    Petrified wood occurs throughout the United States, but some of the most abundant and highest quality examples of these fossils occur in Petrified Forest National Park in eastern Arizona. The park was established as a national monument in 1906. Initially set aside to preserve fossil wood, the area has yielded other prehistoric treasures too.

    On November 28, 2002, the Enhanced Thematic Mapper Plus on NASA’s Landsat 7 satellite captured this natural-color image of Petrified Forest National Park in eastern Arizona. White outlines indicate park boundaries, and thin lines show where a railroad and interstate pass through the park. Sunlight shines from the southeast, casting almost-black shadows on the northern and western slopes, but earth tones dominate this arid area. Colors range from pale pinkish beige to deep rust. In the northern part of the park, the Painted Desert occasionally gives rise to colorful dust storms. To the south, the Blue Mesa region features hoodoos—otherworldly spires topped with big rocks.

    Petrified Forest National Park preserves traces of an ancient, vastly different landscape. Some 225 million years ago, during the Triassic Period, this area rested near Earth’s equator, part of the massive supercontinent Pangaea.Hot and humid, the region was dominated by a huge river system, where horseshoe crabs left footprints in soft stream- and lake-bottom mud. Crocodile-like reptiles; armored, plant-eating reptiles; and Coelophysis—dainty, fleet-footed, meat-eating dinosaurs—all lived here.

    As the park’s name indicates, however, its foremost fossils are petrified logs. Lining abundant waterways, ancient trees occasionally fell into the flowing water, perhaps blown down by winds or killed by insect infestations. While many of the trees rotted away, some were buried by the quick-moving water. When winds carried ash from distant volcanoes, minerals from the ash infiltrated the wood, forming crystals. Crystals occasionally replaced individual cell walls, preserving the petrified wood in detail. Iron and other minerals lent rainbows of color to the petrified trees. Brittle petrified logs often broke into pieces, giving the illusion of ancient trees having been deliberately sawed into segments.

    Over millions of years, newer sediments buried the landscape from the early Triassic, and plate tectonics carried the region away from the equator. But movements in the Earth’s crust also uplifted this area as part of the multistate Colorado Plateau. Younger sediments eventually eroded away, revealing remnants of a vastly different ancient environment.

    1. Reference

    2. National Park Service. (2009, September 16). Petrified Forest. U.S. Department of the Interior. Accessed October 2, 2009.

    NASA image created by Jesse Allen, using park boundary geographic data (GIS) provided the U.S. National Park Servce and Innovative Technology Administration’s Bureau of Transportation Statistics, and Landsat data provided by the United States Geological Survey. Caption by Michon Scott.

    Instrument(s): Landsat 7 - ETM+
     
  6. Torres del Paine National Park

    Grinding glaciers and granite peaks mingle in Chile’s Torres del Paine National Park. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this summertime image of the park on January 21, 2013. This image shows just a portion of the park, including Grey Glacier and the mountain range of Cordillera del Paine… .

    The rivers of glacial ice in Torres del Paine National Park grind over bedrock, turning some of that rock to dust. Many of the glaciers terminate in freshwater lakes, which are rich with glacial flour that colors them brown to turquoise. Skinny rivers connect some of the lakes to each other (image upper and lower right).

    Cordillera del Paine rises between some of the wide glacial valleys. The compact mountain range is a combination of soaring peaks and small glaciers, most notably the Torres del Paine (Towers of Paine), three closely spaced peaks emblematic of the mountain range and the larger park.

    By human standards, the mountains of Cordillera del Paine are quite old. But compared to the Rocky Mountains(up to 70 million years old), and the Appalachians (480 million years), the Cordillera del Paine are very young—only about 12 million years old. study published in 2008 described how scientists used zircon crystals to estimate the age of Cordillera del Paine. The authors concluded that the rock was formed in three pulses, creating a granite laccolith, or dome-shaped feature, more than 2,000 meters (7,000 feet) thick. Later uplift, combined with glacial erosion, created the current mountain range.

    1. References

    2. Michel, J., Baumgartner, L., Putlitz, B., Schaltegger, U., Ovtcharova, M. (2008) Incremental growth of the Patagonian Torres del Paine laccolith over 90 k.y. Geology, 36(6), 459–462.
    3. Rivera, A., Casassa, G. (2004) Ice elevation, areal, and frontal changes of glaciers from national park Torres Del Paine, Southern Patagonia Icefield. Arctic, Antarctic, and Alpine Research, 36(4), 379–389.
    4. Torres del Paine. Accessed January 24, 2013.
    5. U.S. Geological Survey. (2003, May 20) America’s Volcanic Past: Appalachians Mountains. Accessed January 24, 2013.
    6. U.S. Geological Survey. (2004, January 13) Geologic Provinces of the United States: Rocky Mountains. Accessed January 24, 2013.

    NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using Advanced Land Imager data from the NASA EO-1 team. Caption by Michon Scott.

    Instrument(s): EO-1 - ALI
     
  7. Egmont National Park, New Zealand

    Crews aboard the International Space Station recently captured this photograph of the prominent, circular Egmont National Park in New Zealand. The park protects the forested and snow-capped slopes of Mount Egmont. The protected area was designated in 1900, setting up a radius of 10 kilometers (6 miles) centered on the volcanic peak. The curved shoreline of the promontory has been formed by volcanic lava flows spreading out from the volcano on many occasions. In turn, sediments eroding from the coast ring the peninsula with a faint arc of lighter-colored water.

    Also known by its Maori name—Taranaki—Mt. Egmont stands 2,518 meters (8,260 feet) tall and it is one of the world’s most symmetric volcanoes. It first became active about 135,000 years ago. By dating lava flows, geologists have figured out that smaller eruptions at Mount Egmont occur roughly every 90 years and major eruptions every 500 years.

    In the photo, the town of New Plymouth stands out from the surrounding agricultural lands as a gray patch. Other smaller towns stretch out across the plain on the inland side of the volcano. A nadir, or straight-down looking, photo of the volcanowas taken from the space shuttle in 2002.

    Astronaut photograph ISS041-E-049111 was acquired on September 30, 2014, with a Nikon D3S digital camera using a 200 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by the Expedition 41 crew. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by M. Justin Wilkinson, Jacobs.

    Instrument(s): ISS - Digital Camera
     
  8. From Green to Brown

    With temperatures dropping in the northern hemisphere, fall colors swept across the taiga forests of the Kamchatka Peninsula in September and October 2012. Within a span of 11 days, the forests of far eastern Siberia went from green—with only a slight hint of fall color—to a deep brown. Common tree species in the area include Erman’s birch (Betula ermanii), Japanese stone pine (Pinus pumila), and Dahurian larch (Larix daurica).

    The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured the fall transformation in this pair of images from October 1 (top) and September 20, 2012. The forests shown are located near the snow-covered peaks of BezymiannyKlyuchevskaya, and Shiveluch—all active volcanoes.

    In the fall, leaves change colors as they lose chlorophyll, the molecule that plants use to synthesize food. Chlorophyll makes plants appear green because it absorbs the red and blue light from sunlight as it strikes leaf surfaces. However, chlorophyll is not a stable compound and plants have to continuously synthesize it, a process that requires ample sunlight and warm temperatures. So when temperature drop and days shorten in autumn, levels of chlorophyll do as well.

    As concentrations of chlorophyll drop, the green color of leaves fades away, presenting an opportunity for other pigments within leaves—carotenoids and anthocyanins—to show off their colors. Carotenoids absorb blue-green and blue light, so in the absence of chlorophyll, they cause leaves to appear yellow. Anthocyanins absorb blue, blue-green, and green light, so light reflecting off the pigment appears red.

    The range and intensity of autumn colors is strongly affected by the weather. Both low temperatures and bright sunshine destroy chlorophyll. So if the weather stays above freezing, it is easier for anthocyanins to form. Dry weather, which increases the sugar concentration in sap, also increases the amount of anthocyanin. So the brightest autumn colors occur when dry, sunny days are followed by cool, dry nights.

    NASA Earth Observatory image by Robert Simmon, courtesy of the LANCE/EOSDIS MODIS Rapid Response Team, GSFC. Caption by Adam Voiland.

    Instrument(s): Aqua - MODIS
     
  9. Typhoon Vongfong

    When Super Typhoon Vongfong grew to a category 5 storm on October 7, it became the fourth storm of 2014 to reach the top wind-scale classification. It also became the largest storm anywhere on Earth so far in 2014. The name Vongfong means wasp in Cantonese.

    By October 9, the typhoon had weakened somewhat. But the storm also turned north and appeared to be on track to sting Japan by the weekend. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this natural-color image of Vongfong at 1:25 p.m. Japan time (0425 Universal Time) on October 9. By 0600 Universal Time that day, the storm churned the Philippine Sea with maximum sustained winds of 250 kilometers (155 miles) per hour.

    Large, well-defined features in the eye and eyewall are common in storms of this magnitude, noted research meteorologistScott Braun of NASA’s Goddard Space Flight Center. Meteorologist and blogger Jeff Masters reported on October 9 that the storm had developed two concentric eye walls. That means the inner eye wall would likely collapse and be replaced by the outer eye wall—a process expected to cause further weakening. Still, forecasts called for a daunting storm to approach Okinawa and southwest Japan by October 11.

    The storm follows less than one week after Super Typhoon Phanfone charged ashore in Japan’s Shizuoka Prefecture. The copious wind and rain spurred sediment plumes that were visible from space.

    Research shows that between 1971 and 2000, there was an annual average of 26.7 typhoons that developed over the Northwest Pacific Ocean or the South China Sea. Of those, an average of 10.8 reached within 300 kilometers of Japan and 2.6 made landfall each year.

    Typhoon season in the Western and Central Pacific begins June 1 and runs through November.

    NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response Team at NASA GSFC. Caption by Kathryn Hansen.

    Instrument(s): Aqua - MODIS
     
  10. Flooding along the Illinois River

    Autumn usually marks a relatively dry time of year for the region surrounding St. Louis, but the autumn of 2009 brought heavy rains and swollen rivers. The Associated Press reported that heavy rains in late October left thousands of acres of farmland under water, especially in the flat lands of southern and western Illinois, near the Illinois, Ohio, and Kaskaskia Rivers. In early November 2009, the National Weather Service recorded major flooding along the Illinois River.

    The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured these false-color images before and after the storm that flooded the region. The top image is from November 4, 2009, and the bottom image is from October 24, 2009. Both images use a combination of infrared and visible light to increase the contrast between water and land. Vegetation appears bright green, water appears navy blue, and clouds appear pale blue-green.

    In the image acquired November 4, the Mississippi River appears swollen near St. Louis. Roughly 175 kilometers north of the city, the Illinois River is especially wide compared to the same area in late October. Due east of St. Louis, Carlyle Lake, along the Kaskaskia River, has also expanded. Smaller tributaries to the Illinois River also appear flooded.

    East of the Illinois River, vegetation appears less abundant in early November. The change could be the advance of autumn and/or harvesting of agricultural fields, but differences in angle of sunlight (time of day) between the image acquisitions may also play a role.

      1. References

      2. National Weather Service. 
    Lagrange
         and 
    Meredosia.
       National Oceanic and Atmospheric Administration. Accessed November 5, 2009.
    1. Salter, J. (2009, November 3). Missouri, Illinois flooding: Casino, roads closed. Associated Press. Accessed November 5, 2009.

    NASA image courtesy MODIS Rapid Response Team, Goddard Space Flight Center. Caption by Michon Scott, NASA Earth Observatory.

    Instrument(s): Terra - MODIS
     
  11. Expanding Burn Scar in Northern Territory

    The intense bushfires that strike southern Australia in the summer usually attract the most headlines, but the country’s largest and most frequent blazes actually occur in northern Australia in the spring. In fact, in terms of sheer area burned, satellite observations show that over 98 percent of large fires in Australia occur well outside of densely populated southeastern and southwestern parts of the country.

    A fire that began burning in Northern Territory on September 10, 2014, offers a prime example of just how expansive fires from this part of the continent can become. After racing through grasslands for just a few weeks, the fire had charred an area about the size of Massachusetts by October 8, 2014.

    The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this sequence of images showing the progression of the fire. MODIS acquired the top image on September 12, 2014, the middle image on September 23, 2014, and the bottom image on October 7, 2014. Red outlines indicate hot spots where MODIS detected unusually warm surface temperatures associated with fires. Burned areas are dark brown and black.

    The fire appears to have burned in enclosed pasturelands for the first few weeks and then transitioned into desert grasslands to the south. “When you look at the October 7 image, notice that the northern part of the burn scar has edges that appear to follow block fence lines or some other barrier,” explained Rick McRae, a risk analyst for Australia’s Emergency Services Bureau. “But then in the southern part of the scar, you see a distinct change in land cover. You also start to see less regular ‘fractal’ boundaries showing where, each day, there were breakaways driven by prevailing winds.” Since the southern part of the scar is in a desert grassland as opposed to pastureland, the fire had an opportunity to burn naturally in that area, according to McRae.

    Wildfires in this part of Northern Territory are extremely common, with most areas burning every few years. This part of Northern Territory is the third most prolific hotspot-producing region in Australia, according to McRae. “In fact, if you look at the surrounding area, you will see that the entire region is a mosaic of old and large burn scars,” he said.

    NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response Team at NASA GSFC. Caption by Adam Voiland, with information from Daniel Lindsey (NOAA) and Rick McRae (Emergency Services Agency).

    Instrument(s): Terra - MODIS
     
  12. Rhodes, Greece

    Rhodes is the biggest island in the Greek Dodecanese chain in the southeastern Aegean Sea. Rhodes (also known as Rodos) stretches roughly 77 kilometers (48 miles) from northeast to southwest. Its highest point, Mount Attavyros reaches 1,200 meters (3,900 feet) above sea level. A variety of vegetation thrives on the rugged island and migratory birds use it as a resting place. Humans have lived here since the Stone Age.

    The Thematic Mapper on the Landsat 5 satellite captured this image of Rhodes on August 26, 2011. Green vegetation is fairly abundant over the island, except for Mount Attavyros and some spots along the coast.

    Satellite images such as this have provided more than pretty pictures. They have contributed to geologists’ understanding of the island’s history and structure. Geological research of Rhodes is nothing new, as the first studies of the island occurred in the 1850s. More systematic research from 1960 to 1965 resulted in a map issued by the Institute of Geology at the University of Milan, Italy.

    Unfortunately, these studies occurred before the widespread acceptance of plate tectonic theory. Geologists now understand that our planet’s surface is composed of plates that move relative to each other. Rhodes sits in an active area, where the African Plate slides below the Aegean Plate, producing fairly strong earthquakes. Fossils found on Rhodes date back to the late Paleozoic Era before the dinosaurs evolved. The fossils are found inlimestone, indicating that the island of Rhodes was once underwater. Around 15 million years ago, tectonic activity uplifted the whole region, but between 4 million and 3 million years ago, the land sank and left just the mountaintops above water.

    When geologists reexamined Rhodes to create a new map, they not only incorporated advances in geologic theory but also advances in remote sensing. A paper published in 2007 described the compilation of a new geological map of Rhodes based in part on satellite observations by Landsat and by Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite.

    1. References

    2. Landsat Science. (2011, October 26). Rhodes. Accessed January 27, 2012.
    3. RhodesGuide.com. The Dodecanese Islands. Accessed January 27, 2012.
    4. Tsombos, P.I., Nikolakopoulos, K.G., Photiades, A., Psonis, K. (2007). Updating the 1:50.000 geological maps of Rhodes Island using remote sensing data and GIS techniques. Proc. SPIE, 6749, 67491H.
    5. U.S. Geological Survey. (2010, March 29). Tectonic Summary of Greece. Accessed January 27, 2012.
    6. U.S. Geological Survey. (2011, September 19). This Dynamic Earth: The Story of Plate Tectonics. Accessed January 27, 2012.

    NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using Landsat data provided by theUnited States Geological Survey. Caption by Michon Scott.

    Instrument(s): Landsat 5 - TM
     
  13. Milan at Night

    The metropolitan area of Milan (or Milano) illuminates the Italian region of Lombardy in a pattern evocative of a patchwork quilt. The city of Milan forms a dense cluster of lights in this astronaut photograph, with brilliant white lights indicating the historic center of the city where the Duomo di Milano (Milan Cathedral) is located.

    Large dark regions to the south (image left) contain mostly agricultural fields. To the north, numerous smaller cities are interspersed with agricultural fields, giving way to forested areas as one approaches the Italian Alps (not shown). Low, patchy clouds diffuse the city lights, producing isolated regions that appear blurred. The Milan urban area is located within the Po Valley, a large plain bordered by the Adriatic Sea to the east-southeast, the Italian Alps to the north, and the Ligurian Sea and Appenines Mountains to the south.

    Milan has the largest metropolitan area in Italy, and the fifth largest in the European Union. It is one of Europe’s major transportation, industrial, and commercial hubs, and is also a global center of fashion and culture. It is considered an “alpha” world city by the Globalization and World Cities Research Network.

    Astronaut photograph ISS026-E-28829 was acquired on February 22, 2011, with a Nikon D3S digital camera using an effective 200 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 26 crew. The image has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by William L. Stefanov, NASA-JSC.

    Instrument(s): ISS - Digital Camera
     
  14. The Persian Gulf, Clear and Clouded

    These panoramas taken by astronauts from the International Space Station show the tropical blue waters of the Persian Gulf and then the dust-filled skies as a major dust storm obscures the Gulf and its northern shoreline. Strong north winds often blow across the region in summer, churning up dust from the entire length of the deserts in the Tigris and Euphrates valleys (top left in both images). Dust partly obscures hundreds of kilometers of light-green agricultural lands along these rivers in Iraq (left in both images).

    The Caspian Sea cuts across the horizon in the upper image. In the lower image, a line of thunderstorms rises along the edge of the Zagros Mountains of Iran, and the setting sun casts long shadows from those thunderheads. Astronauts see 16 sunrises and sunsets every day from low-Earth orbit, allowing them to capture the dusk darkening a wide variety of landscapes.

    Astronaut photographs ISS040-E-106243 and ISS040-E-113700 were acquired on August 25 and 31, 2014, with a Nikon D3S digital camera using 28 mm and 32 mm lenses respectively. The photos are provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The images were taken by the Expedition 40 crew. They have been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by M. Justin Wilkinson, Jacobs at NASA-JSC.

    Instrument(s): ISS - Digital Camera
     
  15. Floating Pest

    Today’s image is the answer to Earth Observatory’s September Puzzler.

    Popular among water gardeners for its showy flowers and glossy leaves, water hyacinth (Eichhornia crassipes) is one of the fastest-spreading plants in the world. As a result, the floating flower—which is native to the Amazon but now thrives on every continent except Antarctica and Europe—has become one of the most widely reviled, especially in Africa.

    People living along Lake Victoria, the world’s second largest lake, have a particular loathing for water hyacinth. Since the plant became established in the 1990s, occasional outbreaks have caused serious problems for communities bordering the lake, particularly those along Winam Gulf, a shallow inlet in Kenya.

    “This plant has at various times covered so much of the lake, especially in Winam Gulf, that it completely blocked out local fishing, clogged water supplies, and harbored pathogens harmful to local people and animals,” explained University of Nevada–Reno conservation biologist Thomas Albright. “At times, it has been an economic calamity at local and even regional levels.”

    In 1997, an outbreak along the eastern and southern shores of Winam Gulf, carpeted 172 square kilometers (66 square miles) of water with hyacinth. In 2006-2007, heavy rains and nutrient-rich runoff fueled an even more extreme outbreak. The plant-covered area increased from about 40 square kilometers in March 2007 to more than 400 square kilometers just a month later—about one-third of Winam Gulf.

    Aggressive control efforts—including removal by hand or with harvesters on boats, as well as the release of weevils that eat the plant—followed both outbreaks. Ecologists think the weevils can help keep the plant in check, but several other factors affect water hyacinth’s abundance as well. “In the 2000s, we saw big reductions in water hyacinth coverage that we attributed in large part to the effects of an El Niño year with winds, water levels, and wave action possibly uprooting the plants,” Albright said. “The declines we saw in some parts of the lake pre-dated the release of weevils.”

    Though its numbers are down, water hyacinth has hardly been eradicated in Winam Gulf. The Advanced Land Imager (ALI) on the Earth Observing 1 satellite captured this image showing mats of water hyacinths on May 17, 2014, in Osodo Bay, off the Sondu-Miriu Delta. An analysis of nearly a decade of satellite imagery found that this area was one of the most common places for the plant to grow.

    In addition to water hyacinth, blue-green algae and other opportunistic aquatic vegetation—water lettuce, papyrus, and tussock grasses—likely contribute to the green in the image. The water is likely brown with sediment and runoff from recent rains.

    NASA Earth Observatory image by Jesse Allen, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Adam Voiland, with information from Thomas Albright (University of Nevada, Reno) and Thomas Moorhouse (Egerton Unviversity).

    Instrument(s): EO-1 - ALI