Earth Sciences and Image Analysis Photographic Highlights

ISS017 Earth Sciences and Image Analysis Photographic Highlights

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ISS017-E-13025 Tifernine Dune Field, Algeria: The Tifernine Dune Field is located at the southernmost tip of the Grand Erg Oriental, a “dune sea” that occupies a large portion of the Sahara Desert in eastern Algeria. This astronaut photograph illustrates the interface between the yellow-orange sand dunes of the field and dark brown consolidated rocks of the Tinrhert Plateau to the south and east (image right). Three distinct landforms are visible in the image, each providing information about past and present climate in the area.
The oldest landform is represented by the rocks of the Tinrhert Plateau, where numerous channels incise the bedrock; these channels were eroded during a wet and cool climate period, most probably by glacial meltwater streams. As the dry and hot climate that characterizes the Sahara today became established, water ceased to flow in these channels. Winds eroded and moved large amounts of drying sediment (sand, silt, and clay), which piled up in large, linear dunes that roughly parallel the direction of the prevailing winds of the time (image center).
The present climate is still hot and dry, but current wind directions are more variable. The variable winds are modifying the older, linear dunes, creating star dunes, recognizable by a starfish-like pattern when seen from above. White to grey regions within the dune field are exposed deposits of silt and clay, together with evaporite minerals (such as halite, or common table salt) formed by evaporation of water that collected in small basins between the dunes.

ISS017-E-16161 Bouvet Island, South Atlantic Ocean: Bouvet Island (in Norwegian, Bouvetøya) is known as the most remote island in the world; Antarctica, over 1600 kilometers (994 miles) to the south, is the nearest land mass. Located near the junction between the South American, African, and Antarctic tectonic plates, the island is mostly formed from a shield volcano—a broad, gently sloping cone formed by thin, fluid lavas—that is almost entirely covered by glaciers. The prominent Kapp (Cape) Valdivia on the northern coastline is a peninsula formed by a lava dome, a volcanic feature built by viscous lavas with a high silica content. It is only along the steep cliffs of the coastline that the underlaying dark volcanic rock is visible against the white snow and ice blanketing the island.
Bouvet Island was discovered by the French Captain Lozier-Bouvet in 1739, and was subsequently visited by representatives of different nations several times during the nineteenth century. The island was annexed by the Kingdom of Norway in 1927 following a Norwegian expedition’s stay on the island. Bouvet is uninhabited, and its extremely harsh environment precludes anything but short-duration stays. Nevertheless, the island supports some flora (such as lichens) and fauna (seabirds and seals). Abundant sea ice surrounds the island in this astronaut photograph.

ISS017-E-16521 Sandy Cape, Fraser Island, Australia: Fraser Island, the world’s largest sand island, is located along the coastline of Queensland, Australia, and it includes Great Sandy National Park. The island was designated a World Heritage site in 1992, in part due to its outstanding preservation of geological processes related to sand dune formation. The island’s dune fields preserve a record of sand deposition and movement related to sea level rise and fall extending back over 700,000 years. In addition to sand dunes, the island also preserves an interesting range of vegetation—including vine rainforest, stands of eucalpyt trees, and mangroves—and diverse animals, including crabs, parrots, sugar gliders, and flying foxes.
This astronaut photograph highlights the northernmost portion of the island, known as Sandy Cape. Active white sand dunes contrast with dark green vegetation that anchors older dune sets. Irregular patches of sand dunes surrounded by vegetation are known as sand blows (or blowouts), formed when the vegetation cover is disturbed by wind, fire, or human activities. The exposed underlaying sand can then move and form new dunes, sometimes at rates of up to 1 meter/year. Coastal sand dune fields, such as the one located along the eastern side of Sandy Cape (center), will remain active until anchored by vegetation, or until no more sand is available to form new dunes.

ISS017-E-18044 Coronado Island and the Gulf of California, Mexico: Located in the Bahia de los Angeles—Bay of the Angels—Isla Coronado (Coronado Island, also known as “Smith Island” on some maps) sits in the Gulf of California, just off the eastern shoreline of Mexico. The island is approximately 7 km long, and is dominated by Volcan (volcano) Coronado on the northern end. The date of last eruption of the volcano is not known, but gas and steam activity was last recorded in 1539.
Coronado Island—together with nearby Isla Mitlan and Isla Calavera—has an arid climate and is sparsely vegetated. Despite the harshness of the environment, sea lion colonies can be found on the island, and the Bahia de los Angeles is a popular sport fishing location. Partly in response to increased environmental pressure on the islands from both fishing and tourism, local groups developed a management and conservation plan for the islands in the bay, with international support, in the late 1990s.
The island is an important piece of the ecology of the Gulf of California. In 1940, marine biologist Ed Ricketts, together with his friend, author John Steinbeck, conducted an expedition and collecting trip in the Sea of Cortez (now known as the Gulf of California) to explore the rich ecology of the intertidal zone. Coronado Island and the Bahia de los Angeles were part of that expedition. The resulting book by Steinbeck and Ricketts, Sea of Cortez, remains a classic document of the natural history and ecology of the Gulf of California. At the time, the marine environment around Coronado appeared to Ricketts and Steinbeck as sterile (in their words, “burned”) compared to the rest of the Gulf.
Today, the uninhabited island is a refuge with a rich marine assemblage, especially when compared to other unprotected parts of the Gulf. This image provides hints of the diverse marine environment around the island. Most of the coast is steep and rocky, but lighter blue lagoons, especially along the western coast, provide shallower, protected environments that are biologically robust. Offshore, internal waves and complex surface currents facilitate mixing of the water, important for nutrient delivery to the coastal environments. These features “observed as patterns in the water” are outlined by the sunglint (light reflecting off of the water surface back towards the camera onboard the International Space Station). The sunglint patterns are due to wind and currents, which roughen the water surface and enhance reflection, and surfactants that decrease the surface tension and roughness, resulting in regions of dark smooth water.

ISS017-E-13789 Desert Erosion, A Modern Libyan Landscape: This detailed astronaut photograph shows the classic patterns of an eroded desert landscape, about 300 kilometers (190 miles) south of Libya’s Mediterranean coast. Widespread indented patterns are low escarpments and stream terraces generated by stream erosion—on those few occasions in any decade when enough rain falls for streams to flow. The only areas where sediment is being deposited are the streambeds, which appear in this image as sinuous zones with a distinct component of black minerals. These minerals give the streambeds a darker color than adjacent low escarpments (image top left and lower left). The sediment comes from a volcanic landscape immediately upstream to the west.
Other stream-generated features are several relict stream banks (indicated by ovals); one area even preserves both (parallel) banks of the original stream (far right oval). The ancient stream banks were cemented by minerals such as calcium carbonate and gypsum, introduced by the streams when they were active, probably during wetter climates in the past 2 million years. Relict stream courses show prior positions of streams, and help tell the region’s paleoclimate story. They also provide Earth analogs for similar features on Mars.
The lack of vegetation is the first indication of the great aridity of the region, but sand dunes also appear as sinuous lines oriented perpendicular to the dominant northeasterly wind direction (transverse dunes). If the dominant wind direction remains the same, these transverse dunes would be expected to move further to the southwest over time (towards the top left). Some of the dunes cross the river courses, showing how seldom the rivers flow.

ISS017-E-18075 Pueblo Chemical Depot, Colorado: This astronaut photograph illustrates the unusual man-made landscape of the Pueblo Chemical Depot located near the city of Pueblo, Colorado. The depot was built during World War II by the U.S. Army to house and ship ammunition needed for war efforts, and this role transitioned to missile repair and maintenance during the Cold War with the Soviet Union. The current use of the depot is to house chemical munitions, but changes are underway by the U.S. Army Chemical Materials Agency to destroy these munitions and make the site environmentally safe for reuse.
The stippled pattern on the landscape is due to hundreds of concrete and earth-covered storage “igloos” that form ordered rows across the site (image top). These igloos are where chemical munitions and other materials are secured. Larger, white-roofed maintenance buildings once used for munitions storage were built with separate compartments to minimize potential damage from explosions. Other features visible in this detailed image include roads (light tan lines) and rail lines (dark brown), water impoundments (black, irregular shapes), and various office and industrial buildings (rectangular shapes at image lower left.)

ISS017-E-20538 Arkenu Craters, Libya: Geologists often study features on Earth, such as impact craters, to gain insight into processes that occur on other planets. On Earth, more than 150 impact craters have been identified on the continents, but only a few of these are classified as double impact craters. One such pair, the Arkenu Craters in northern Africa, is shown in this image. Arkenu 1 and 2 are double impact structures located in eastern Libya in the Sahara Desert (22 degrees, 4 minutes North; 23 degrees, 45 minutes East). Their respective diameters are approximately 6.8 and 10.3 kilometers (4.2 and 6.4 miles). The craters are unusual in that they both exhibit concentric annular ridge structures (white circles in the image outline the position of the outermost visible ridges). In many terrestrial craters these features are highly eroded and no longer visible.
While the circular structure of these features had been noted, the impact origin hypothesis was strengthened in December 2003 when a field team observed shatter cones—cone-shaped features in rocks created by the shock generated during impact. The field research team also observed large outcrops of impact breccias—a jumble of rock fragments generated at the impact site that are now cemented together into an identifiable rock layer. One theory of the craters’ formation proposes they were the result of two impactors, each approximately 500 meters in diameter. The age of the impact event has been dated as having occurred less than 140 million years ago.
While the presence of shatter cones and impact breccias is generally considered to be strong evidence for meteor impact, some scientists now question the interpretation of these features observed at the Arkenu structures. They suggest that the features were caused by erosive and volcanic processes. At present, both craters are being crossed by linear dunes extending northeast-southwest (image upper left to center right). The superposition of the dunes across the annular ridges indicates that they are much younger than the craters.

ISS017-E-19616 Dust Storm, Turkmenistan, Central Asia: This west-looking astronaut photograph, taken with a short focal length lens from the International Space Station, spans a wide swath of central Asia—from Afghanistan, along the length of Turkmenistan, and beyond to the Caspian Sea. Winds blowing down the largest river valley in the region, the Amudarya, were strong enough to raise a large dust storm. Dust appears as a light brown mass extending into the center of the image from the lower right. Diffuse dust from prior windy weather appears over much of the area making a regional haze that hides landscape details. The haze partly obscures the irrigated agriculture in Turkmenistan and entirely obscures the Caspian Sea.
Numerous rivers rise in the Hindu Kush range (lower left). The Band-i Amir River is a major tributary of the main regional river, the Amudarya, which it reaches via a deep canyon. The Amudarya River was the major historical contributor of water to the Aral Sea, but today extensive diversion of river water for agricultural purposes has led to desiccation of the sea bed. The exposed sea bed is a major source of saline dusts contaminated with agricultural chemicals, and it poses a significant environmental and human health hazard to central Asia. To a lesser extent, dusts are also mobilized from sediments along the Amudarya River channel.
The Paropamisus Range and the Amudarya (also known as the Oxus River) are mentioned in histories of Alexander the Great’s famous military expedition from Greece to India. His horsemen are described as having made a fast side excursion from near the Caspian Sea (image top right) as far as the Amudarya (image lower right).

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ISS017-E-13025	Tifernine Dune Field, Algeria: The Tifernine Dune Field is located at the southernmost tip of the Grand Erg Oriental, a “dune sea” that occupies a large portion of the Sahara Desert in eastern Algeria. This astronaut photograph illustrates the interface between the yellow-orange sand dunes of the field and dark brown consolidated rocks of the Tinrhert Plateau to the south and east (image right). Three distinct landforms are visible in the image, each providing information about past and present climate in the area. The oldest landform is represented by the rocks of the Tinrhert Plateau, where numerous channels incise the bedrock; these channels were eroded during a wet and cool climate period, most probably by glacial meltwater streams. As the dry and hot climate that characterizes the Sahara today became established, water ceased to flow in these channels. Winds eroded and moved large amounts of drying sediment (sand, silt, and clay), which piled up in large, linear dunes that roughly parallel the direction of the prevailing winds of the time (image center). The present climate is still hot and dry, but current wind directions are more variable. The variable winds are modifying the older, linear dunes, creating star dunes, recognizable by a starfish-like pattern when seen from above. White to grey regions within the dune field are exposed deposits of silt and clay, together with evaporite minerals (such as halite, or common table salt) formed by evaporation of water that collected in small basins between the dunes.
ISS017-E-16161	Bouvet Island, South Atlantic Ocean: Bouvet Island (in Norwegian, Bouvetøya) is known as the most remote island in the world; Antarctica, over 1600 kilometers (994 miles) to the south, is the nearest land mass. Located near the junction between the South American, African, and Antarctic tectonic plates, the island is mostly formed from a shield volcano—a broad, gently sloping cone formed by thin, fluid lavas—that is almost entirely covered by glaciers. The prominent Kapp (Cape) Valdivia on the northern coastline is a peninsula formed by a lava dome, a volcanic feature built by viscous lavas with a high silica content. It is only along the steep cliffs of the coastline that the underlaying dark volcanic rock is visible against the white snow and ice blanketing the island. Bouvet Island was discovered by the French Captain Lozier-Bouvet in 1739, and was subsequently visited by representatives of different nations several times during the nineteenth century. The island was annexed by the Kingdom of Norway in 1927 following a Norwegian expedition’s stay on the island. Bouvet is uninhabited, and its extremely harsh environment precludes anything but short-duration stays. Nevertheless, the island supports some flora (such as lichens) and fauna (seabirds and seals). Abundant sea ice surrounds the island in this astronaut photograph.
ISS017-E-16521	Sandy Cape, Fraser Island, Australia: Fraser Island, the world’s largest sand island, is located along the coastline of Queensland, Australia, and it includes Great Sandy National Park. The island was designated a World Heritage site in 1992, in part due to its outstanding preservation of geological processes related to sand dune formation. The island’s dune fields preserve a record of sand deposition and movement related to sea level rise and fall extending back over 700,000 years. In addition to sand dunes, the island also preserves an interesting range of vegetation—including vine rainforest, stands of eucalpyt trees, and mangroves—and diverse animals, including crabs, parrots, sugar gliders, and flying foxes. This astronaut photograph highlights the northernmost portion of the island, known as Sandy Cape. Active white sand dunes contrast with dark green vegetation that anchors older dune sets. Irregular patches of sand dunes surrounded by vegetation are known as sand blows (or blowouts), formed when the vegetation cover is disturbed by wind, fire, or human activities. The exposed underlaying sand can then move and form new dunes, sometimes at rates of up to 1 meter/year. Coastal sand dune fields, such as the one located along the eastern side of Sandy Cape (center), will remain active until anchored by vegetation, or until no more sand is available to form new dunes.
ISS017-E-18044	Coronado Island and the Gulf of California, Mexico: Located in the Bahia de los Angeles—Bay of the Angels—Isla Coronado (Coronado Island, also known as “Smith Island” on some maps) sits in the Gulf of California, just off the eastern shoreline of Mexico. The island is approximately 7 km long, and is dominated by Volcan (volcano) Coronado on the northern end. The date of last eruption of the volcano is not known, but gas and steam activity was last recorded in 1539. Coronado Island—together with nearby Isla Mitlan and Isla Calavera—has an arid climate and is sparsely vegetated. Despite the harshness of the environment, sea lion colonies can be found on the island, and the Bahia de los Angeles is a popular sport fishing location. Partly in response to increased environmental pressure on the islands from both fishing and tourism, local groups developed a management and conservation plan for the islands in the bay, with international support, in the late 1990s. The island is an important piece of the ecology of the Gulf of California. In 1940, marine biologist Ed Ricketts, together with his friend, author John Steinbeck, conducted an expedition and collecting trip in the Sea of Cortez (now known as the Gulf of California) to explore the rich ecology of the intertidal zone. Coronado Island and the Bahia de los Angeles were part of that expedition. The resulting book by Steinbeck and Ricketts, Sea of Cortez, remains a classic document of the natural history and ecology of the Gulf of California. At the time, the marine environment around Coronado appeared to Ricketts and Steinbeck as sterile (in their words, “burned”) compared to the rest of the Gulf. Today, the uninhabited island is a refuge with a rich marine assemblage, especially when compared to other unprotected parts of the Gulf. This image provides hints of the diverse marine environment around the island. Most of the coast is steep and rocky, but lighter blue lagoons, especially along the western coast, provide shallower, protected environments that are biologically robust. Offshore, internal waves and complex surface currents facilitate mixing of the water, important for nutrient delivery to the coastal environments. These features “observed as patterns in the water” are outlined by the sunglint (light reflecting off of the water surface back towards the camera onboard the International Space Station). The sunglint patterns are due to wind and currents, which roughen the water surface and enhance reflection, and surfactants that decrease the surface tension and roughness, resulting in regions of dark smooth water.
ISS017-E-13789	Desert Erosion, A Modern Libyan Landscape: This detailed astronaut photograph shows the classic patterns of an eroded desert landscape, about 300 kilometers (190 miles) south of Libya’s Mediterranean coast. Widespread indented patterns are low escarpments and stream terraces generated by stream erosion—on those few occasions in any decade when enough rain falls for streams to flow. The only areas where sediment is being deposited are the streambeds, which appear in this image as sinuous zones with a distinct component of black minerals. These minerals give the streambeds a darker color than adjacent low escarpments (image top left and lower left). The sediment comes from a volcanic landscape immediately upstream to the west. Other stream-generated features are several relict stream banks (indicated by ovals); one area even preserves both (parallel) banks of the original stream (far right oval). The ancient stream banks were cemented by minerals such as calcium carbonate and gypsum, introduced by the streams when they were active, probably during wetter climates in the past 2 million years. Relict stream courses show prior positions of streams, and help tell the region’s paleoclimate story. They also provide Earth analogs for similar features on Mars. The lack of vegetation is the first indication of the great aridity of the region, but sand dunes also appear as sinuous lines oriented perpendicular to the dominant northeasterly wind direction (transverse dunes). If the dominant wind direction remains the same, these transverse dunes would be expected to move further to the southwest over time (towards the top left). Some of the dunes cross the river courses, showing how seldom the rivers flow.
ISS017-E-18075	Pueblo Chemical Depot, Colorado: This astronaut photograph illustrates the unusual man-made landscape of the Pueblo Chemical Depot located near the city of Pueblo, Colorado. The depot was built during World War II by the U.S. Army to house and ship ammunition needed for war efforts, and this role transitioned to missile repair and maintenance during the Cold War with the Soviet Union. The current use of the depot is to house chemical munitions, but changes are underway by the U.S. Army Chemical Materials Agency to destroy these munitions and make the site environmentally safe for reuse. The stippled pattern on the landscape is due to hundreds of concrete and earth-covered storage “igloos” that form ordered rows across the site (image top). These igloos are where chemical munitions and other materials are secured. Larger, white-roofed maintenance buildings once used for munitions storage were built with separate compartments to minimize potential damage from explosions. Other features visible in this detailed image include roads (light tan lines) and rail lines (dark brown), water impoundments (black, irregular shapes), and various office and industrial buildings (rectangular shapes at image lower left.)
ISS017-E-20538	Arkenu Craters, Libya: Geologists often study features on Earth, such as impact craters, to gain insight into processes that occur on other planets. On Earth, more than 150 impact craters have been identified on the continents, but only a few of these are classified as double impact craters. One such pair, the Arkenu Craters in northern Africa, is shown in this image. Arkenu 1 and 2 are double impact structures located in eastern Libya in the Sahara Desert (22 degrees, 4 minutes North; 23 degrees, 45 minutes East). Their respective diameters are approximately 6.8 and 10.3 kilometers (4.2 and 6.4 miles). The craters are unusual in that they both exhibit concentric annular ridge structures (white circles in the image outline the position of the outermost visible ridges). In many terrestrial craters these features are highly eroded and no longer visible. While the circular structure of these features had been noted, the impact origin hypothesis was strengthened in December 2003 when a field team observed shatter cones—cone-shaped features in rocks created by the shock generated during impact. The field research team also observed large outcrops of impact breccias—a jumble of rock fragments generated at the impact site that are now cemented together into an identifiable rock layer. One theory of the craters’ formation proposes they were the result of two impactors, each approximately 500 meters in diameter. The age of the impact event has been dated as having occurred less than 140 million years ago. While the presence of shatter cones and impact breccias is generally considered to be strong evidence for meteor impact, some scientists now question the interpretation of these features observed at the Arkenu structures. They suggest that the features were caused by erosive and volcanic processes. At present, both craters are being crossed by linear dunes extending northeast-southwest (image upper left to center right). The superposition of the dunes across the annular ridges indicates that they are much younger than the craters.
ISS017-E-19616	Dust Storm, Turkmenistan, Central Asia: This west-looking astronaut photograph, taken with a short focal length lens from the International Space Station, spans a wide swath of central Asia—from Afghanistan, along the length of Turkmenistan, and beyond to the Caspian Sea. Winds blowing down the largest river valley in the region, the Amudarya, were strong enough to raise a large dust storm. Dust appears as a light brown mass extending into the center of the image from the lower right. Diffuse dust from prior windy weather appears over much of the area making a regional haze that hides landscape details. The haze partly obscures the irrigated agriculture in Turkmenistan and entirely obscures the Caspian Sea. Numerous rivers rise in the Hindu Kush range (lower left). The Band-i Amir River is a major tributary of the main regional river, the Amudarya, which it reaches via a deep canyon. The Amudarya River was the major historical contributor of water to the Aral Sea, but today extensive diversion of river water for agricultural purposes has led to desiccation of the sea bed. The exposed sea bed is a major source of saline dusts contaminated with agricultural chemicals, and it poses a significant environmental and human health hazard to central Asia. To a lesser extent, dusts are also mobilized from sediments along the Amudarya River channel. The Paropamisus Range and the Amudarya (also known as the Oxus River) are mentioned in histories of Alexander the Great’s famous military expedition from Greece to India. His horsemen are described as having made a fast side excursion from near the Caspian Sea (image top right) as far as the Amudarya (image lower right).

This service is provided by the International Space Station program and the JSC Astromaterials Research & Exploration Science Directorate. Recommended Citation: Image Science and Analysis Laboratory, NASA-Johnson Space Center. "The Gateway to Astronaut Photography of Earth." .
	NASA Responsible Official: Tracy Calhoun Curator: jsc-earthweb@mail.nasa.gov Contributors: Earth Sciences Web Team	National Aeronautics and Space Administration Lyndon B. Johnson Space Center	International Space Station National Laboratory Last Update:
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