Earth Sciences and Image Analysis Photographic Highlights

ISS032 Earth Sciences and Image Analysis Photographic Highlights

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ISS032-E-24687 Idaho Fires, September 2012: Taken with a short lens (45 millimeters), this west-looking astronaut photograph has a field of view covering much of the forested region of central Idaho. The dark areas are wooded mountains—the Salmon River Mountains (image left), the Bitterroots (lower right) and Clearwater Mountains (right). All three areas experienced wildfires in September 2012.
Smaller fire “complexes” appear as tendrils of smoke near the sources—for example, the Halstead fires—and as major smoke plumes from fires in the densest forests—such as the Mustang fire complex. Mustang produced the largest plume in the region, with thick smoke blowing eastward over the Beaverhead Mountains (image bottom).
The linear shape of the smoke plumes gives a sense of the generally eastward smoke transport on September 3, 2012. (Note that the image is rotated so that north is to the right.) The smoke distribution also reveals another kind of transport. At night, when winds are weak, the cooling of the atmosphere near the ground causes cooler, denser air to drain down into the valleys. On September 3, this led to some smoke flowing west, down into the narrow Salmon and Lochsa River valleys—in the opposite direction from the higher winds and the thick smoke masses.
Beyond the fires, the bright yellow-tan areas at image top left and right are grasslands (including the Palouse Grasslands Ecoregion). Light green areas in many of the valleys are agricultural crops, including barley, alfalfa, and wheat. The largest single wilderness area in the contiguous United States, the Frank Church-River of No Return Wilderness, occupies the wooded zones of the Salmon River Mountains and the Clearwater Mountains—most of the area shown in the middle of the image. And the Continental Divide cuts through the bottom of the image—rivers on the eastern slopes of the Beaverhead Mountains drain to the Atlantic Ocean, while rivers in the rest of the area drain to the Pacific Ocean.

ISS032-E-9123 Pyramids at Giza, Egypt: The Great Pyramids at Giza are the last of the Seven Wonders of the Ancient World and perhaps the most famous of the ancient monuments in the Nile River Delta of Egypt. They are also a favorite subject of photography from orbit—particularly when high-resolution imagery can be obtained. This subset of a larger astronaut photograph illustrates the degree of detail visible from the International Space Station (ISS) using a long focal-length lens to provide high magnification. With good illumination of the scene and a steady hand on the camera, current off-the-shelf digital cameras on the ISS can acquire detailed images to rival those of automated satellite sensors.
The southeast-facing sides of the pyramids of the pharaohs Khufu, Khafre, and Menkaure are all brightly illuminated by the Sun, while the northwest facing sides are in shadow. This shadowing also highlights smaller, unfinished pyramids to the south of Menkaure’s pyramid and fields of rectangular, flat-roofed mastabas (tombs) to the east and west of Khufu’s pyramid. While not as grand as the pyramids, mastabas were the burial places of prominent people during the time of the ancient pharaohs. To the southeast of Khufu’s pyramid, the head and rear haunches of the Sphinx are also visible (albeit not clearly).
It is a short distance between the glories of ancient Egypt and the modern Cairo metropolitan area to the north and east. The green vegetation of a hotel golf course (image right) and the numerous buildings and streets of El Giza provide stark contrast to the bare rock and soil of the adjacent desert. Roadways visible in the desert (image left) connect the urban regions to the east with further development to the north (not shown).

ISS032-E-17635 Kuwait City at Night: Seen at night, Kuwait City contrasts dramatically with the dark surface of the Persian Gulf and the sparsely populated desert. Night views also show some aspects of urban geography that are difficult to perceive in daylight images. Here the focus of radial traffic arteries and “ring roads” guide the eye toward the financial center of Kuwait’s capital—on the cape extending into Kuwait Bay, north of the First Ring Road. The numbering of the ring roads shows the progressive southward development of the city towards the Seventh Ring Road, which still lies outside the built-up area.
The differences in the color of city lighting also provide information on the urban geography. Areas with lighting of a yellow-green tinge are newer residential districts. The town of Al Ahmadi, known for its verdant vegetation, was built in 1946 when oil was discovered; it stands out with a characteristic blue-white light. Kuwait International Airport, like most major airports around the world, is particularly bright due to the high concentration of lights. By contrast, the low residential density of the Emir’s palace grounds—which also host Kuwaiti government offices and a large mosque—stand out as a dark area within the city. The long, dark zone facing the Persian Gulf coast, just inshore of a narrow zone of coastal villas (image right), is being prepared for residential construction.

ISS032-E-17547 Istanbul at Night: Most of Istanbul’s Asian suburbs (image right) appear in this night view from the International Space Station, but only about half the area of the city on the European side is visible. The margins of the metropolitan area are clearly visible at night, more so than in daylight images in daylight images.
The Bosporus strait (also spelled Bosphorus) famously separates the two halves of the city and links the small Sea of Marmara (and the Mediterranean Sea) to the Black Sea. The strait is 31 kilometers (19 miles) long, most of which is visible in this view. The Bosporus is a very busy waterway, with larger ships passing north-south between the Black Sea and the Mediterranean, while competing with numerous ferries that cross east-west between the two halves of the city.
Apart from the Sea of Marmara and Black Sea, the other dark areas are wooded hills that provide open spaces for the densely populated city—one of the largest in Europe at 13.5 million inhabitants. The old city of Istanbul occupies the prominent point at the southern entrance to the strait. The brighter lines crossing the metropolitan area the major traffic arteries; bright lights also mark the shorelines. The First Bosporus Bridge and Second Bridge (also known as the Fatih Sultan Mehmet Bridge) span the strait. The brilliant lights of both international airports also stand out at image lower left and image lower right.

ISS032-E-10482 Sutter Buttes, California: Sometimes called the “smallest mountain range in the world,” the Sutter Buttes rise almost 610 meters (2,000 feet) above the flat agricultural fields of the Great Valley of central California. The Sutter Buttes are remnants of a volcano that was active approximately 1.6 to 1.4 million years ago during the Pleistocene Epoch. The central core of the Buttes is characterized by lava domes—piles of viscous lava that erupted onto the surface and were built higher with each successive layer. Today, these lava domes form the high central hills of the Buttes; shadows cast by the hills are visible at image center.
Surrounding the core is an apron of fragmental material created by occasional eruptions of the lava domes. This apron extends roughly 18 kilometers east-to-west and 16 kilometers north-to-south (11 by 10 miles). The volcanic material was transported outwards from the central core by volcanic gas-driven pyroclastic flows or by cooler, water-driven lahars. Later stream erosion of the debris apron is evident from the drainage pattern surrounding the central core. A third geomorphic region of valleys, known as the “moat,” lies between the core and the debris apron, and was formed by erosion of older, exposed sedimentary rocks that underlie the volcanic rocks.
The Sutter Buttes present a striking visual contrast with the surrounding agricultural fields—mostly rice, with some sunflower, winter wheat, tomato, and almonds—of the Great Valley. Urban areas such as Yuba City, California (located 18 kilometers/11 miles to the southeast) appear as light to dark gray stippled regions. Sacramento, California, (not shown) is located approximately 80 kilometers (50 miles) to the south-southeast. The image appears slightly distorted (oblique) due to the viewing angle from the International Space Station.
A more detailed description of the geology of the Sutter Buttes is available here (PDF).

ISS032-E-16579 Strandplain, Coastal Peru: The scale and orientation of landscape features that are difficult to see from the ground often become readily visible from orbit. Numerous subparallel lines along the arid, northern coast of Peru are close-packed beach ridges, known collectively as a strandplain. (For scale, the strandplain is 30 kilometers long.) Each ridge shows the position of a prior shoreline. The Chira River delta appears at image right, with dark green agricultural fields occupying the area. A smaller river reaches the sea, without forming a delta, at image left. The prominent cape at lower left is Punta Balcones, a region with many oil wells.
Strandplains are built by successive additions of beach sand, usually from some nearby source. Currents on this coast of South America (about 5 degrees south of the Equator) come from the south, suggesting that the Chira River delta is the source of the sand. The newest beach is being formed today by the waves—which appear as the thin, ragged white line along the strandplain—supplied by the north-flowing current. The regularity of the spacing of the beaches suggests that some episodic influx of sediment controls beach formation. This influx may be determined by floods coming down the Chira River, possibly driven by the heavy rains of El Nino events, which occur irregularly every few years.
Two other sets of faint parallel lines can be seen on higher ground inland (marked with arrows), with the upper set stretching all the way from the Chira river floodplain. Observed in many places along the coast of Peru, these also may be strandplains generated when the land surface was at a lower elevation. Both also may have been produced by sand from the Chira River. The land surface is known to be rising along this coast with the rise of the Andes Mountains, which explains why the upper shorelines now lie 120 meters above sea level.

ISS032-E-10487 Walker Lake, Nevada: The Pleistocene landscape of western Nevada (about 15,000 years ago) was one of narrow mountain ranges and numerous interconnected lakes that together formed the glacial Lake Lahontan. The drying and warming of the regional climate since the last Ice Age led to the disappearance of the glaciers that provided meltwater and, eventually, to the disappearance of Lake Lahontan itself. Today, few remnants of Lahontan remain; most of its arms have become dry, enclosed basins known as playas.
This astronaut photograph highlights Walker Lake, one of only two remnants of Lake Lahontan that contain water throughout the year. (Pyramid Lake in Nevada is the other.) Walker Lake is located in an enclosed basin, bounded by the Wassuk Range to the west and the Gillis Range to the east. The lake is fed by the Walker River, which flows in from the north. The current dimensions of the lake are approximately 21 kilometers (13 miles) north-to-south by 9 kilometers (6 miles) east-to-west. Shoreline deposits form concentric bands that are just visible in the image; these rings record the varying lake levels when the water was higher in the geologic past.
The nearest town to Walker Lake is Hawthorne, Nevada. To the southwest, the highest peak of the Wassuk Range—Mount Grant (3,496 meters above sea level)—dominates the skyline. Green agricultural fields, primarily alfalfa, to the west of the Wassuk Range provide a striking contrast to the surrounding Great Basin desert. These fields are irrigated using water from the nearby East Fork of the Walker River.

ISS032-E-6129 Krymsk, Krasnodar region, Southern Russia: On the night of July 7, 2012, a major storm dumped more than a foot (30 centimeters) of water on the Krasnodar area of southern Russia, near the Black Sea. The resulting flood was likened to a tsunami, and to date more than 170 people have died, most in the city of Krymsk. The Moscow Times reports that more than 19,000 people lost everything.
This image, taken by cosmonauts aboard the International Space Station, shows the city of Krymsk on July 10, 2012. For context, an aerial view from July 7 (inset) shows the flooding of the Kuban River tributary, which flows through the center of the city. Regions that were flooded along the channel have tan to brown color in the ISS image, likely due to the mud and debris that was left behind by the floodwaters.
Krymsk is located in the western foothills on the northern slope of the Caucasus Mountains, a range that stretches between the Black Sea and the Caspian Sea. The vast amount of rain quickly overwhelmed the small river channels that flow north from the mountains to the Russian lowlands and the Kuban River. Krymsk was directly in the pathway of the flash flood.
As part of the international partner agreement to use the International Space Station to benefit humanity, crew members and other Earth observing instruments provide support to the International Disaster Charter (IDC) by collecting imagery of areas impacted by natural events such as flooding. Data may be accessed through the IDC web site’s Charter Geographic Tool for use in relief efforts or to communicate more clearly the geographic impacts of events through annotated maps.

ISS032-E-8976 Sahara Dust Reaches the Americas: Weather satellites frequently document dust palls blowing westward from Africa’s Sahara Desert across the tropical Atlantic Ocean. Astronauts see these Saharan dust masses as widespread atmospheric haze. The dust can be transported right across the Atlantic Ocean, taking about a week to reach North America (in northern hemisphere summer) or South America (in northern hemisphere winter). This puts the Caribbean Sea on the receiving end of many of these events.
In the top image, the margin of hazy air reaches the island of Hispaniola (Haiti and Dominican Republic) and the Turks and Caicos Islands, though the eastern tip of Cuba (foreground) remains clear. This image—taken by astronauts on the International Space Station (ISS) in July 2012—attracted the interest of scientists at NASA’s Johnson Space Center because the margin between dust haze and clear atmosphere lies in almost the same location as it appeared in another astronaut image in July 1994. When astronauts aboard the Space Shuttle Columbia captured the lower image (rotated from the 2012 view), few scientists had considered the possibility of trans-Atlantic dust transport.
The Columbia image also shows the brilliant blues of the shallow banks surrounding the Caicos Island in the Bahamas. The mountainous spine of Haiti lies further away, partly obscured by dust. Closer to the foreground—about 26 degrees north latitude—the skies are clear.
The dust in the images is almost 8,000 kilometers from its likely source in northern Mali, although data from sensors such as the Total Ozone Mapping Spectrometer and Ozone Monitoring Instrument have suggested that some dust traveling across the Atlantic may originate even further east in Chad or Sudan. Once airborne, Saharan dust has been known to travel west all the way into the Pacific Ocean, crossing Mexico at the narrow Isthmus of Tehuantepec.
We now know that African dust reaches the western hemisphere every month of the year, though not necessarily in as visible a form as in these images. Researchers have linked Saharan dust to coral disease, allergies in humans, and harmful algal blooms (“red tides”). There is also evidence that some of this African dust serves as a source of airborne nutrients for Amazon rainforest vegetation.

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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: Susan Runco

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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ISS032-E-24687	Idaho Fires, September 2012: Taken with a short lens (45 millimeters), this west-looking astronaut photograph has a field of view covering much of the forested region of central Idaho. The dark areas are wooded mountains—the Salmon River Mountains (image left), the Bitterroots (lower right) and Clearwater Mountains (right). All three areas experienced wildfires in September 2012. Smaller fire “complexes” appear as tendrils of smoke near the sources—for example, the Halstead fires—and as major smoke plumes from fires in the densest forests—such as the Mustang fire complex. Mustang produced the largest plume in the region, with thick smoke blowing eastward over the Beaverhead Mountains (image bottom). The linear shape of the smoke plumes gives a sense of the generally eastward smoke transport on September 3, 2012. (Note that the image is rotated so that north is to the right.) The smoke distribution also reveals another kind of transport. At night, when winds are weak, the cooling of the atmosphere near the ground causes cooler, denser air to drain down into the valleys. On September 3, this led to some smoke flowing west, down into the narrow Salmon and Lochsa River valleys—in the opposite direction from the higher winds and the thick smoke masses. Beyond the fires, the bright yellow-tan areas at image top left and right are grasslands (including the Palouse Grasslands Ecoregion). Light green areas in many of the valleys are agricultural crops, including barley, alfalfa, and wheat. The largest single wilderness area in the contiguous United States, the Frank Church-River of No Return Wilderness, occupies the wooded zones of the Salmon River Mountains and the Clearwater Mountains—most of the area shown in the middle of the image. And the Continental Divide cuts through the bottom of the image—rivers on the eastern slopes of the Beaverhead Mountains drain to the Atlantic Ocean, while rivers in the rest of the area drain to the Pacific Ocean.
ISS032-E-9123	Pyramids at Giza, Egypt: The Great Pyramids at Giza are the last of the Seven Wonders of the Ancient World and perhaps the most famous of the ancient monuments in the Nile River Delta of Egypt. They are also a favorite subject of photography from orbit—particularly when high-resolution imagery can be obtained. This subset of a larger astronaut photograph illustrates the degree of detail visible from the International Space Station (ISS) using a long focal-length lens to provide high magnification. With good illumination of the scene and a steady hand on the camera, current off-the-shelf digital cameras on the ISS can acquire detailed images to rival those of automated satellite sensors. The southeast-facing sides of the pyramids of the pharaohs Khufu, Khafre, and Menkaure are all brightly illuminated by the Sun, while the northwest facing sides are in shadow. This shadowing also highlights smaller, unfinished pyramids to the south of Menkaure’s pyramid and fields of rectangular, flat-roofed mastabas (tombs) to the east and west of Khufu’s pyramid. While not as grand as the pyramids, mastabas were the burial places of prominent people during the time of the ancient pharaohs. To the southeast of Khufu’s pyramid, the head and rear haunches of the Sphinx are also visible (albeit not clearly). It is a short distance between the glories of ancient Egypt and the modern Cairo metropolitan area to the north and east. The green vegetation of a hotel golf course (image right) and the numerous buildings and streets of El Giza provide stark contrast to the bare rock and soil of the adjacent desert. Roadways visible in the desert (image left) connect the urban regions to the east with further development to the north (not shown).
ISS032-E-17635	Kuwait City at Night: Seen at night, Kuwait City contrasts dramatically with the dark surface of the Persian Gulf and the sparsely populated desert. Night views also show some aspects of urban geography that are difficult to perceive in daylight images. Here the focus of radial traffic arteries and “ring roads” guide the eye toward the financial center of Kuwait’s capital—on the cape extending into Kuwait Bay, north of the First Ring Road. The numbering of the ring roads shows the progressive southward development of the city towards the Seventh Ring Road, which still lies outside the built-up area. The differences in the color of city lighting also provide information on the urban geography. Areas with lighting of a yellow-green tinge are newer residential districts. The town of Al Ahmadi, known for its verdant vegetation, was built in 1946 when oil was discovered; it stands out with a characteristic blue-white light. Kuwait International Airport, like most major airports around the world, is particularly bright due to the high concentration of lights. By contrast, the low residential density of the Emir’s palace grounds—which also host Kuwaiti government offices and a large mosque—stand out as a dark area within the city. The long, dark zone facing the Persian Gulf coast, just inshore of a narrow zone of coastal villas (image right), is being prepared for residential construction.
ISS032-E-17547	Istanbul at Night: Most of Istanbul’s Asian suburbs (image right) appear in this night view from the International Space Station, but only about half the area of the city on the European side is visible. The margins of the metropolitan area are clearly visible at night, more so than in daylight images in daylight images. The Bosporus strait (also spelled Bosphorus) famously separates the two halves of the city and links the small Sea of Marmara (and the Mediterranean Sea) to the Black Sea. The strait is 31 kilometers (19 miles) long, most of which is visible in this view. The Bosporus is a very busy waterway, with larger ships passing north-south between the Black Sea and the Mediterranean, while competing with numerous ferries that cross east-west between the two halves of the city. Apart from the Sea of Marmara and Black Sea, the other dark areas are wooded hills that provide open spaces for the densely populated city—one of the largest in Europe at 13.5 million inhabitants. The old city of Istanbul occupies the prominent point at the southern entrance to the strait. The brighter lines crossing the metropolitan area the major traffic arteries; bright lights also mark the shorelines. The First Bosporus Bridge and Second Bridge (also known as the Fatih Sultan Mehmet Bridge) span the strait. The brilliant lights of both international airports also stand out at image lower left and image lower right.
ISS032-E-10482	Sutter Buttes, California: Sometimes called the “smallest mountain range in the world,” the Sutter Buttes rise almost 610 meters (2,000 feet) above the flat agricultural fields of the Great Valley of central California. The Sutter Buttes are remnants of a volcano that was active approximately 1.6 to 1.4 million years ago during the Pleistocene Epoch. The central core of the Buttes is characterized by lava domes—piles of viscous lava that erupted onto the surface and were built higher with each successive layer. Today, these lava domes form the high central hills of the Buttes; shadows cast by the hills are visible at image center. Surrounding the core is an apron of fragmental material created by occasional eruptions of the lava domes. This apron extends roughly 18 kilometers east-to-west and 16 kilometers north-to-south (11 by 10 miles). The volcanic material was transported outwards from the central core by volcanic gas-driven pyroclastic flows or by cooler, water-driven lahars. Later stream erosion of the debris apron is evident from the drainage pattern surrounding the central core. A third geomorphic region of valleys, known as the “moat,” lies between the core and the debris apron, and was formed by erosion of older, exposed sedimentary rocks that underlie the volcanic rocks. The Sutter Buttes present a striking visual contrast with the surrounding agricultural fields—mostly rice, with some sunflower, winter wheat, tomato, and almonds—of the Great Valley. Urban areas such as Yuba City, California (located 18 kilometers/11 miles to the southeast) appear as light to dark gray stippled regions. Sacramento, California, (not shown) is located approximately 80 kilometers (50 miles) to the south-southeast. The image appears slightly distorted (oblique) due to the viewing angle from the International Space Station. A more detailed description of the geology of the Sutter Buttes is available here (PDF).
ISS032-E-16579	Strandplain, Coastal Peru: The scale and orientation of landscape features that are difficult to see from the ground often become readily visible from orbit. Numerous subparallel lines along the arid, northern coast of Peru are close-packed beach ridges, known collectively as a strandplain. (For scale, the strandplain is 30 kilometers long.) Each ridge shows the position of a prior shoreline. The Chira River delta appears at image right, with dark green agricultural fields occupying the area. A smaller river reaches the sea, without forming a delta, at image left. The prominent cape at lower left is Punta Balcones, a region with many oil wells. Strandplains are built by successive additions of beach sand, usually from some nearby source. Currents on this coast of South America (about 5 degrees south of the Equator) come from the south, suggesting that the Chira River delta is the source of the sand. The newest beach is being formed today by the waves—which appear as the thin, ragged white line along the strandplain—supplied by the north-flowing current. The regularity of the spacing of the beaches suggests that some episodic influx of sediment controls beach formation. This influx may be determined by floods coming down the Chira River, possibly driven by the heavy rains of El Nino events, which occur irregularly every few years. Two other sets of faint parallel lines can be seen on higher ground inland (marked with arrows), with the upper set stretching all the way from the Chira river floodplain. Observed in many places along the coast of Peru, these also may be strandplains generated when the land surface was at a lower elevation. Both also may have been produced by sand from the Chira River. The land surface is known to be rising along this coast with the rise of the Andes Mountains, which explains why the upper shorelines now lie 120 meters above sea level.
ISS032-E-10487	Walker Lake, Nevada: The Pleistocene landscape of western Nevada (about 15,000 years ago) was one of narrow mountain ranges and numerous interconnected lakes that together formed the glacial Lake Lahontan. The drying and warming of the regional climate since the last Ice Age led to the disappearance of the glaciers that provided meltwater and, eventually, to the disappearance of Lake Lahontan itself. Today, few remnants of Lahontan remain; most of its arms have become dry, enclosed basins known as playas. This astronaut photograph highlights Walker Lake, one of only two remnants of Lake Lahontan that contain water throughout the year. (Pyramid Lake in Nevada is the other.) Walker Lake is located in an enclosed basin, bounded by the Wassuk Range to the west and the Gillis Range to the east. The lake is fed by the Walker River, which flows in from the north. The current dimensions of the lake are approximately 21 kilometers (13 miles) north-to-south by 9 kilometers (6 miles) east-to-west. Shoreline deposits form concentric bands that are just visible in the image; these rings record the varying lake levels when the water was higher in the geologic past. The nearest town to Walker Lake is Hawthorne, Nevada. To the southwest, the highest peak of the Wassuk Range—Mount Grant (3,496 meters above sea level)—dominates the skyline. Green agricultural fields, primarily alfalfa, to the west of the Wassuk Range provide a striking contrast to the surrounding Great Basin desert. These fields are irrigated using water from the nearby East Fork of the Walker River.
ISS032-E-6129	Krymsk, Krasnodar region, Southern Russia: On the night of July 7, 2012, a major storm dumped more than a foot (30 centimeters) of water on the Krasnodar area of southern Russia, near the Black Sea. The resulting flood was likened to a tsunami, and to date more than 170 people have died, most in the city of Krymsk. The Moscow Times reports that more than 19,000 people lost everything. This image, taken by cosmonauts aboard the International Space Station, shows the city of Krymsk on July 10, 2012. For context, an aerial view from July 7 (inset) shows the flooding of the Kuban River tributary, which flows through the center of the city. Regions that were flooded along the channel have tan to brown color in the ISS image, likely due to the mud and debris that was left behind by the floodwaters. Krymsk is located in the western foothills on the northern slope of the Caucasus Mountains, a range that stretches between the Black Sea and the Caspian Sea. The vast amount of rain quickly overwhelmed the small river channels that flow north from the mountains to the Russian lowlands and the Kuban River. Krymsk was directly in the pathway of the flash flood. As part of the international partner agreement to use the International Space Station to benefit humanity, crew members and other Earth observing instruments provide support to the International Disaster Charter (IDC) by collecting imagery of areas impacted by natural events such as flooding. Data may be accessed through the IDC web site’s Charter Geographic Tool for use in relief efforts or to communicate more clearly the geographic impacts of events through annotated maps.
ISS032-E-8976	Sahara Dust Reaches the Americas: Weather satellites frequently document dust palls blowing westward from Africa’s Sahara Desert across the tropical Atlantic Ocean. Astronauts see these Saharan dust masses as widespread atmospheric haze. The dust can be transported right across the Atlantic Ocean, taking about a week to reach North America (in northern hemisphere summer) or South America (in northern hemisphere winter). This puts the Caribbean Sea on the receiving end of many of these events. In the top image, the margin of hazy air reaches the island of Hispaniola (Haiti and Dominican Republic) and the Turks and Caicos Islands, though the eastern tip of Cuba (foreground) remains clear. This image—taken by astronauts on the International Space Station (ISS) in July 2012—attracted the interest of scientists at NASA’s Johnson Space Center because the margin between dust haze and clear atmosphere lies in almost the same location as it appeared in another astronaut image in July 1994. When astronauts aboard the Space Shuttle Columbia captured the lower image (rotated from the 2012 view), few scientists had considered the possibility of trans-Atlantic dust transport. The Columbia image also shows the brilliant blues of the shallow banks surrounding the Caicos Island in the Bahamas. The mountainous spine of Haiti lies further away, partly obscured by dust. Closer to the foreground—about 26 degrees north latitude—the skies are clear. The dust in the images is almost 8,000 kilometers from its likely source in northern Mali, although data from sensors such as the Total Ozone Mapping Spectrometer and Ozone Monitoring Instrument have suggested that some dust traveling across the Atlantic may originate even further east in Chad or Sudan. Once airborne, Saharan dust has been known to travel west all the way into the Pacific Ocean, crossing Mexico at the narrow Isthmus of Tehuantepec. We now know that African dust reaches the western hemisphere every month of the year, though not necessarily in as visible a form as in these images. Researchers have linked Saharan dust to coral disease, allergies in humans, and harmful algal blooms (“red tides”). There is also evidence that some of this African dust serves as a source of airborne nutrients for Amazon rainforest vegetation.

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: Susan Runco 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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