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The Calabrian Peninsula appears shortened and distorted due to the extreme sideways viewing angle from the ISS. Such a perspective is termed oblique, as opposed to a nadir view, in which the astronaut is looking directly downwards towards the Earth’s surface from the ISS. This highly oblique view also highlights two distinct cloud patterns over the Calabrian interior. Patchy, highly textured cumulus clouds are present at lower altitudes, while grey altostratus clouds are stretched out by prevailing winds at higher altitudes. The Strait of Messina, just visible at image upper right, marks the boundary between the coastline of Italy and the island of Sicily.
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Two major types of dunes are visible in the image. Large, roughly north-south oriented transverse dunes fill the image frame. This type of dune tends to form at roughly right angles to the dominant, northeasterly winds. The dune crests are marked in this image by darker, steeper sand accumulations that cast shadows. The lighter-toned zones between are lower, interdune “flats.” The large dunes appear to be highly symmetrical with regard to their crests. This pattern suggests that the crest sediments are coarser, preventing the formation of a steeper slip face on the downwind side of the dune by wind-driven motion of similarly sized sand grains.
This particular form of transverse dune is known as a zibar, and it is thought to form by winnowing of smaller sand grains by the wind, which leaves the coarser grains to form dune crests. A second set of thin linear dunes oriented at roughly right angles to the zibar dunes appears to be formed on the larger landforms and is therefore a younger landscape feature. These dunes appear to be forming from finer grains in the same wind field as the larger zibars.
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While the grey-brown surface of the salar is flat and desiccated, mineral-rich brines—water with a high percentage of dissolved salts—are located below the surface. The subsurface brines of the Salar de Atacama are particularly rich in lithium salts. Lithium is an essential component of advanced batteries and medicines.
The brines are pumped to the surface through a network of wells and into large, shallow evaporation ponds; three such evaporation facilities are visible in the center of the image. Color variations in the ponds are due to varying amounts of salts relative to water. The dry and windy climate enhances evaporation of the water, leaving concentrated salts behind for extraction of the lithium.
This astronaut photograph illustrates the central portion of the Salar de Atacama. It is bounded by brown to grey-brown folded and faulted rock layers of the Cordillera de la Sal to the northwest (image upper left) and darker bedrock of the Cordón de Lila to the south (image lower right).
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The Giens Peninsula is formed from two tombolos. A tombolo is a ridge of beach material (typically sand), built by wave action, that connects an island to the mainland. Tombolos, like many coastal features, typically change dramatically over geologic time due to fluctuating sediment supply, coastal currents, sea levels and storm events. The tombolos of the Giens Peninsula have been modified by human activities, as well, including sand dune removal, construction of roadways, and replacement of the original sand by other materials. The long-term survival of these tombolos will be determined by the effects of these changes on the natural coastal processes, with potential sea level rise presenting an additional threat.
In addition to Giens, three other urban areas are visible in this image: Carqueiranne, Hyères, and La Londe-les-Maures. The urban areas are recognizable by both light pink rooftops and grey street grids. These colors contrast with green to brown vegetated areas, including agricultural fields between Hyères and La Londe-les-Maures and more natural vegetation (dark green) on hills between Hyères and Carqueiranne. Small white dots and streaks in the Mediterranean Sea are yachts and other recreational boats.
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Besides being the seat of government, Bridgetown is the largest city in Barbados. It and the surrounding towns that make up the Greater Bridgetown area are located along the southwestern coastline of the island. The metropolitan area is readily recognizable in this astronaut photograph due to the gray and white rooftops and street grids (image center) that contrast with green vegetated fields and riverside areas of the island’s interior to the northeast (image top center).
Bridgetown is a major port destination for both commercial and cruise ships serving the eastern Caribbean—several ships are visible within Carlisle Bay. Water color in the image changes from light blue along the coastline—indicating shallow water—to the dark blue of deeper water away from the island.
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Because of the present arid climate, few people have ever seen the Tsauchab River with flowing water or a lake in Sossus Vlei. In times past, however, the Tsauchab appears to have reached the Atlantic coast, another 55 kilometers farther west. Like several other rivers of the coastal Namib Desert, the Tsauchab brings sediment down from the hinterland to the coastal lowland. This sediment is then blown from the river beds, and over probably tens of millions of years, has accumulated as the red dunes of the impressive Namib Sand Sea.
This astronaut photo shows sand heaped up in numerous star dunes, each of them with long arms extending in several directions. Unlike crescent-shaped barchan dunes, which form in areas where winds generally blow from one direction, star dunes are apparently generated where winds are variable. In this part of the Namib Sand Sea, winds are mainly from the south, but easterly winds, channeled along the Tsauchab valley, provide another component. And warm dry winter winds—similar to the Santa Ana winds of California—blow from the northeast.
These northeasterly winds are likely responsible for the regular dune arms that point into the valley from both sides. These large dunes facing the river valley are promoted as the highest dunes in the world. Although continuous dune slopes allow hikers to ascend to altitudes more than 300 meters above the river bottom, not all of that elevation gain has to be walked; the main base of the dunes lies on a terrace 180 meters above the river.
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Palm Jumeirah (image lower left) was begun in 2001 and required more than 50 million cubic meters of dredged sand to raise the islands above the Persian Gulf sea level. Construction of the Palm Jumeirah islands was completed in 2006; the islands are now being developed for residential and commercial housing and infrastructure. Creation of the 300 World Islands (image upper right) was begun in 2003 and completed in 2008, using 320 million cubic meters of sand and 37 million tonnes of rock for the surrounding 27-kilometer-long protective breakwater. Little to no infrastructure development of The World is apparent in this astronaut photograph.
Also visible at the lower edge of the astronaut photograph is another notable structure—the Burj Khalifa (image lower right and rotated 90 degrees in inset). Burj Khalifa stands 800 meters (2,600 feet) high, and it is currently the world’s tallest structure. The astronaut photograph captures enough detail to make out the tapering outline of the building as well as its dark, needle-like shadow pointing towards the northeast.
An earlier astronaut photograph shows an early phase of construction of Palm Jumeirah. The Earth Observatory’s World of Change feature also tracks urbanization in Dubai.
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This astronaut photograph illustrates three open-pit mines located west-northwest of the town of Green Valley, Arizona. While the mines appear to be close to each other, each exploits a separate porphyry copper deposit. A porphyry copper deposit forms when crystal-rich magma moves upwards through pre-existing rock layers. As the magma cools and crystallizes, it forms an igneous rock with large crystals embedded in a fine-grained matrix, known as porphyry. Hot fluids circulate through the magma and surrounding rocks via fractures, depositing copper-bearing and other minerals in characteristic spatial patterns that signal the nature of the ore body to a geologist.
The mine pits are recognizable by the concentric lines of benches cut into the pit sides. The benches allow equipment and personnel access to the fresh ore (gray) exposed at the bottom of the excavation. Water may also pool at the bottom of inactive pits, such as in the Twin Buttes Mine at image upper right (black areas). The open pit areas are surrounded by an array of sculpted tailings ponds and mine dump areas; these receive mine waste rock for storage and later leaching for further recovery of metals. The green color of the water in the tailings pond at image right is likely due to the presence of leached metals.
The Asarco-Mission complex (image left) is an active producer of copper and molybdenum (important in making steel and other metal alloys), processing approximately 53,700 tons of ore per day (as of 2008). The Twin Buttes Mine (image top right), also a producer of copper and molybdenum, was closed in 1994 but was recently purchased by a new owner (Freeport-McMoRan Copper & Gold) and may reopen. The Sierrita Mine at image lower right (also owned by Freeport-McMoRan Copper & Gold) produces copper, molybdenum, and the rare metal rhenium. Rhenium is used to make high-temperature alloys for jet engine parts and in high-octane, lead-free gasoline. This mine can process over 115,000 tons of ore per day (as of 2007).
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The main channel of the river, flowing south at this point—sixty kilometers south of the city of Choele Choel (not shown)—appears in partial sun glint at image right. Sun glint occurs when light is reflected off a water surface directly back towards the viewer, like a mirror, imparting a silvery sheen to those areas. When meander scars contain water they are known as oxbow lakes, some of which are also highlighted by sun glint in the image.
The orange tint to the water in one of the oxbow lakes (image center) could result from orange salt-loving algae. Their appearance here would be unusual since floodplain lakes are usually too fresh for algae blooms. But an explanation may lie in the location of the Rio Negro on the margin of Argentina’s arid Patagonian region, where annual rainfall is less than 300 millimeters (12 inches). Evaporation in this cloudless region could be high enough for some lakes to become salty.
The Rio Negro flows generally southeast from the Andes Mountains to the Atlantic Ocean. Its floodplain supports the biggest pear- and apple-growing region of Argentina. Rectangular farm boundaries can be seen at bottom center in the image. The river also hosts the world’s longest kayak regatta, which lasts six days. During the 1800s, the river was also the demarcation line between farmlands of European settlers and territory controlled by indigenous people.
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Polar mesospheric clouds are also known as noctilucent or “night-shining” clouds—a property that is clearly visible in this astronaut photograph. The clouds exhibit thin, wispy light blue forms that contrast with the darkness of space (image upper right). Lower levels of the clouds are more strongly illuminated by the Sun and appear light orange to white. Clouds closest to the Earth’s surface are reddish-orange (image center).
The image was taken approximately 38 minutes after midnight Greenwich Mean Time (GMT), while the International Space Station was located over the southern Atlantic Ocean. At this time of year, the Sun never sets over Antarctica, but rather traces an arc across the local horizon, allowing polar mesospheric clouds to be observed near local midnight.
The International Space Station (ISS) orbit ranges from 52 degrees north to 52 degrees south; combined with the highly oblique (“from-the-side”) views through the Earth’s atmosphere that are possible with hand-held cameras, the ISS is an ideal platform for documenting transient, high-altitude phenomena like polar mesospheric clouds. Another NASA mission, the Aeronomy of Ice in the Mesosphere is dedicated to the study of polar mesospheric clouds, and the satellite is providing daily information about their formation, distribution, and variability.
