Earth Sciences and Image Analysis Photographic Highlights

ISS015 Earth Sciences and Image Analysis Photographic Highlights

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ISS015-E-5624 Springtime Comes to the Niagara River:
(image is paired with/compared to image ISS014-E-17999)

What a difference a month makes! These two images of the Niagara River draining Lake Erie (bottom) into Lake Ontario (top) were acquired about a month apart (March 21 and April 29, 2007, respectively) from the International Space Station. The pair documents the breakup of the Lake Erie ice pack, the unofficial signature of spring for residents of Buffalo and Niagara Falls. In March, the eastern end of Lake Erie is clogged with ice that is pushed against the shoreline by the prevailing westerly wind. The ice collects in Lake Erie, and the Lake Erie-Niagara River Ice Boom prevents it from flowing down the Niagara River, which is the international boundary between the Canadian Province of Ontario, and New York State.

The 2,680-meter (8,800-foot) boom is deployed each December. Operational since 1964, the boom serves several functions: it protects the water intakes for the Niagara River power plants, and it minimizes ice runs (large blocks of ice flowing downstream as ice breaks up in the spring) and blockages that can create damage and flooding along the river. At the height of winter, the thickness of the ice at the Buffalo harbor can reach 3.5 meters (12 feet). The removal of the ice boom, usually in early April, is now marked by local celebrations. This year the boom was removed in mid-April, a bit later than usual. A webcam allows remote viewers to monitor ice pack at the boom.

During their missions, astronauts track the changing seasons using such indicators as the springtime melting of ice packs in high-latitude oceans and lakes. Over the next two years, the space station astronauts will make these types of observations to support International Polar Year (IPY) investigations. Scientists interested in requesting high-latitude imagery from the space station for IPY science should visit the Johnson Space Center Gateway to Astronaut Photography of the Earth International Polar Year Website.

ISS015-E-7543 Concepcion Volcano, Nicaragua: Concepción Volcano one of the tallest and most active of Nicaragua’s volcanoes. The 1,610-meter (5,280-foot), cone-shaped volcano is the northern half of dumbbell-shaped Isla de Ometepe. Concepción is joined by a narrow isthmus to the dormant Maderas Volcano, which makes up the southern half of the island. This image of the volcano was captured on May 10, 2007, by the astronauts onboard the International Space Station. To the northwest of the crater, a very faint plume (probably steam) creeps like fog down the mountain, blurring the sharp gullies that carve the volcano’s flanks. The grid pattern of people’s fields surrounds the volcano, while lobes of forest line the lower slopes.

Concepción has erupted at least 25 times in the past 125 years, but eruptions are not the only hazard for the 5,000 or so people who lives in small towns at lower elevations. Loose rock and ash from previous eruptions makes the volcano’s steep slopes unstable and prone to give way during heavy rains. These flows of muddy debris are known as lahars. Among the most serious lahars that have occurred at Concepción in recent years were those that occurred during the passage of Hurricane Mitch through the area in 1998. (Much more serious lahars occurred at Nicaragua’s Casita Volcano during Hurricane Mitch.) The gullies that can funnel debris quickly downslope into populated areas are obvious in the image.

References and Related images:
Lahar Hazards at Concepción Volcano, Nicaragua, a U.S. Geological Survey Webpage
Wide-area view of western Nicaragua, including Lake Nicaragua and Isla Ometepe at lower right, from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite

ISS015-E-5977 Den Helder, Netherlands: The city and harbor of Den Helder in the northern Netherlands has been the home port of the Dutch Royal Navy for over 175 years. The location provides access to the North Sea, which has made it an important commercial and strategic port. Bright red agricultural fields to the south of Den Helder indicate another noteworthy aspect of the region—commercial farming of tulips and hyacinth. This astronaut photograph is an oblique view (an angled, not a “straight down”view) of the Den Helder region taken from the International Space Station (ISS). The ISS was located to the southeast, near Dülmen, Germany, when the image was acquired, about 225 kilometers (140 miles) away in terms of ground distance.
In addition to the urban structures of the Den Helder area (reddish-gray to gray street grids) and dockyards to the east of the city, several striking natural features are visible. The prominent branching pattern of the extensive gray mudflats (image bottom right) indicate that this image was acquired at low tide, and show the generally low elevation of the region. Parallel wave patterns along the mudflats and in the Marsdiep Strait are formed as water interacts with the sea bottom between Den Helder and Texel Island during tidal flow. (Some ship wakes are also visible.) The bright, white-gray triangular region at the southern tip of Texel Island (image upper left) is a dune field, consisting mainly of eolian (wind-borne) sands deposited during the last ice age. Subsequent sea level rise and shoreline processes have shifted these sands into their current configuration, which includes a new dune field island to the southwest of Texel.

ISS015-E-8920 Southern Everglades National Park, Florida: Everglades National Park in southern Florida is the largest subtropical wilderness in the United States. Known as the “river of grass,” the Everglades wetlands and wooded uplands host a variety of endangered species including crocodiles, manatees, and panthers. During the late nineteenth and twentieth centuries, the original 11,000 square miles of wetlands were viewed as useless swampland in need of reclamation. The success of reclamation efforts—for agriculture and urban expansion in southern Florida—has led to the loss of approximately 50 percent of the original wetlands and 90 percent of wading bird species. Today, an extensive restoration effort is underway to return portions of the Everglades to a more natural state and prevent further ecosystem degradation.
This astronaut photograph highlights the southern Everglades, where the wetlands meet Florida Bay. Thin fingers of land and small islands (keys) host mangrove, hardwood hammocks (tree-covered mounds), marsh and prairie (mainly dark to light green in the image). The tan and grayish-brown areas at image upper right are dominantly scrub, marshland and prairie; small green “dots” and narrow lines in this region are isolated mangrove and hardwood stands indicating the general direction of slow water flow toward the bay. The silver-gray regions at image left are water surfaces highlighted by sunglint, light reflected off the water surface directly back towards the astronaut aboard the International Space Station. The roadway forming the western boundary of the National Park is U.S. Route 1, which connects the Miami metropolitan area to the north (not shown) with the Florida Keys to the south (not shown). A small tan patch visible along the roadway is a fishing camp.

ISS015-E-10125 Iceberg A22A, South Atlantic Ocean:
(image is paired with/compared to image ISS015-E-10118)

This astronaut photograph illustrates the remains of a giant iceberg—designated A22A— that broke off Antarctica in 2002. The iceberg was photographed on May 30 at a location of 49.9 degrees south latitude, 23.8 degrees west longitude, which is about a third of the distance from South America towards Cape Town, South Africa. A22A is one of the largest icebergs to drift as far north as 50 degrees south latitude, bringing it beneath the daylight path of the International Space Station (ISS). Crew members aboard the ISS were able to locate the ice mass and photograph it, despite the great masses of clouds that often accompany winter storms in the Southern Ocean. The crew’s viewing angle was oblique (not looking straight down) from a point to the west of the berg, and the time of day was early afternoon, as shown by the orientation of the cloud shadows. Dimensions of A22A in early June were 49.9 by 23.4 kilometers, giving it an area of 622 square kilometers, or seven times the area of Manhattan Island.

Images of the iceberg are being acquired from the ISS to support a study of massive icebergs—part of NASA International Polar Year activities. The study will increase understanding of the way ice sheets evolve as climate changes. When large masses of ice float into warmer waters north of their usual latitudes, they undergo change at rapidly increased rates. Changes that would take decades to occur in Antarctica can happen in a few years or even months in the warmer conditions at 50 degrees south latitude. The crew of the ISS will continue to collect imagery of the accelerating breakup of iceberg A22A as weather, orbital, and illumination conditions allow.

More information, including Webcams, on the studies conducted on A22 and at other places in the Antarctic can be found at www.thistle.org and the National Snow and Ice Data Center’s Icetrek Website (http://nsidc.org/icetrek/).

ISS015-E-10704 Grey Glacier, Chile: The Southern Patagonian Icefield of Chile and Argentina hosts several spectacular glaciers—including Grey Glacier located in the Torres del Paine National Park in Chile. This glacier, which in 1996 had a measured total area of 270 square kilometers and a length of 28 kilometers (104 square miles in area, 17 miles long), begins in the Patagonian Andes Mountains to the west and terminates in three distinct lobes into Grey Lake (upper image). The upper image is a photograph taken by an astronaut aboard the International Space Station, and it captures a striking blue coloration of the glacier. The coloring is due to the ice’s absorption of red wavelengths of light and scattering of blue wavelengths of light as it is transmitted through the ice.
Certain portions of the glacier visible in the image are indeed gray. Linear gray-brown moraines are accumulations of soil and rock debris that form along the edges of a glacier as it flows downhill across the landscape (much like a bulldozer blade). Glaciers flowing downslope through adjacent feeder valleys ultimately meet, and debris entrained along their sides becomes concentrated in the central portion of the resulting single, large glacier—much as smaller streams of water join to form a single large river. Three of these medial moraines are visible in the ice mass at image center left.

Gray-brown patches of debris from adjacent mountainsides color the surface of the easternmost lobe of the glacier (image top). Several crevasse fields are visible in the image. The crevasses, each a small canyon in the ice, form as a result of stress between slower- and faster-moving ice within the glacier. The crevasse patterns of Grey Glacier are complex, perhaps due to the three-lobed nature of its terminus, or end, into Grey Lake. The rugged surface of the glacier is also demonstrated by the jagged shadows it casts onto the surface of the lake.

The astronaut photograph, acquired in 2007, is compared with a false-color image from the Landsat 5 satellite captured in 1986. The false-color image highlights glacier ice in bright blue (lower image). Vegetation is bright green, and bare ground is pink. The general position of the glacier’s terminus in 2007 is marked with yellow lines on the 1986 image. All three lobes have retreated over the 22-year period, with the greatest loss of ice occurring along the westernmost lobe terminus. Grey Glacier, like others in southern Patagonia, loses ice from its terminus as it enters the water, a process known as calving. Calving produces large free-floating chunks of ice; some floating ice is visible near the central glacier lobe in the upper image. The observed retreat means that ice loss has been greater than ice replenishment. It is most likely due to a combination of increased regional temperatures and changes in precipitation amounts.

ISS015-E-5481 Patuxent River Naval Air Station, Maryland: Maryland’s Patuxent River Naval Air Station is located on a small peninsula, bordered by the Patuxent River to the north-northeast and Chesapeake Bay to the east and southeast. The air station was commissioned in 1943, replacing farmlands that had occupied the peninsula less than a year earlier. The primary purpose of “Pax River” (as the site is known by the U.S. Navy) was to consolidate geographically dispersed testing facilities that existed prior to World War II. The Patuxent River station is now the primary center for naval air technology research, development, testing, and support, as well as being the location of the Navy Test Pilot School.
International Space Station crews frequently use the Patuxent River Naval Air Station as a geographic reference point and photographic training target. This astronaut photograph illustrates why—the distinctive pattern of the airfield runways and the station’s location in Chesapeake Bay make it easy to spot from orbit. The sharp boundaries between different kinds of land surfaces are good for camera focusing practice.

This particular image also captures surface water current patterns around the peninsula. Wind- and wave-roughened water surfaces appear silver-gray due to increased reflectance of light back towards the camera (sunglint), whereas dark blue water patches indicate water smoothed by the presence of oils and surfactants (smooth water reflects less light back to the observer) from either natural or human sources. A zone of mixing from converging shoreline currents extends northeast into the bay from Cedar Point.

ISS015-E-5815 Algae in Great Salt Lake: The Great Salt Lake of northern Utah is a remnant of glacial Lake Bonneville that extended over much of present-day western Utah and into the neighboring states of Nevada and Idaho approximately 32,000 to 14,000 years ago. During this time, the peaks of adjacent ranges such as the Promontory and Lakeside Mountains were most likely islands. As climate warmed and precipitation decreased in the region, glaciers that fed meltwater to Lake Bonneville disappeared, and the lake began to dry up. The present-day Great Salt Lake is a terminal lake in that water does not flow out of the lake basin. Water loss through the year is due primarily to evaporation, and when this loss exceeds input of water from rivers, streams, precipitation, and groundwater, the lake level decreases. This is particularly evident during droughts.
Evaporation and the relatively shallow water levels (maximum lake depth is around 33 feet), has led to increased salinity (dissolved salt content). The north arm of the lake, displayed in this astronaut photograph from April 30, 2007, typically has twice the salinity of the rest of the lake due to impoundment of water by a railroad causeway that crosses the lake from east to west. The causeway restricts water flow, and the separation has led to a striking division in the types of algae and bacteria found in the north and south arms of the lake. North of the causeway, the red algae Dunaliella salina and the bacterial species Halobacterium produce a pronounced reddish cast to the water, whereas south of the causeway, the water color is dominated by green algae such as Dunaliella viridis. The Great Salt Lake also supports brine shrimp and brine flies; and it is a major stopover point for migratory birds including avocets, stilts, and plovers.

ISS015-E-5983 Upheaval Dome, Utah: Upheaval Dome is a striking geologic structure in the Canyonlands National Park of southern Utah. Viewed from directly above (and on geologic maps), the alternating rock layers make a nearly circular, 5.5-kilometer- (3.4-mile-) diameter “bull’s-eye.” The oldest rocks are in the center (Chinle and Moenkopi Formations, with limited exposures of even older rocks), and progressively younger rocks are exposed farther out: Wingate Sandstone, Kayenta Formation, and Navajo Sandstone (in order of decreasing age). This kind of rock formation—a fold in the Earth’s crust in which the rocks slope downward from either side of a central point—is called an anticline. If the exposed rock layers form a closed circle at the surface, the anticline is called a dome. It is typical of these formations for the central rocks to be the oldest.
This photograph of Upheaval Dome was taken by an astronaut onboard the International Space Station. The oblique viewing angle—in other words, not looking straight down—provides a sense of the topography within and around the structure. The dome appears more like an ellipse than a circle due to the oblique viewing perspective. Dark regions in the image are cloud and cliff shadows.

Scientists propose at least two ideas about how Upheaval Dome formed. Some believe that the dome is a sign of a sub-surface salt dome—a rising plug of relatively low-density salt that caused overlying rock layers to dome up in a circular pattern like a basketball underneath a blanket. The overlying rock layers were uplifted and then eroded, leaving the bull’s-eye surface pattern.

Another hypothesis identifies Upheaval Dome as an impact structure, caused by a meteor striking the Earth approximately 60 million years ago. In this interpretation, the erosion-resistant Navajo and Wingate Sandstones define multiple crater rings, while the Chinle, Moenkopi, and older rocks exposed in the middle of the dome are the central peak of the impact structure. Debate about the origin of Upheaval Dome continues; recent evidence—such as microscale deformations of the rocks and minerals that are consistent with a high-energy impact event—lends support to the impact-structure hypothesis.

ISS015-E-5483 Brooklyn, New York Waterfront: This astronaut photograph captures the dense urban fabric of Brooklyn, New York City’s largest borough (population of 2.6 million), characterized by the regular pattern of highly reflective building rooftops (white). Two main arteries from Manhattan into Brooklyn—the famous Brooklyn Bridge and neighboring Manhattan Bridge—cross the East River along the left (north) side of the image. The densely built-up landscape contrasts with the East River and Upper New York Bay (image lower right) waterfront areas, recognizable by docks and large industrial loading facilities that extend across the image center from left to right. Much of the shipping traffic has moved to the New Jersey side of New York Bay, a shift that has spurred dismantling and redevelopment of the historic dockyards and waterfront warehouses into residential properties. However, efforts to conserve historic buildings are also ongoing.
The original name for Brooklyn, Breukelen, means “broken land” in Dutch, perhaps in recognition of the highly mixed deposits (boulders, sand, silt, and clay) left behind by the Wisconsin glacier between 20,000 and 90,000 years ago. These deposits form much of Long Island, of which Brooklyn occupies the western tip. This image features one of Brooklyn’s largest green spaces, the Green-Wood Cemetery. The green canopy of the cemetery’s trees contrasts sharply with the surrounding urban land cover. Today, the cemetery also functions as a natural park, and it is an Audubon Sanctuary. Also visible in the image is Governors Island, which served as a strategic military installation for the U.S. Army (1783–1966) and a major U.S. Coast Guard installation (1966–1996). Today the historic fortifications on the island and their surroundings comprise the Governors Island National Monument.

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ISS015-E-5624	Springtime Comes to the Niagara River: (image is paired with/compared to image ISS014-E-17999) What a difference a month makes! These two images of the Niagara River draining Lake Erie (bottom) into Lake Ontario (top) were acquired about a month apart (March 21 and April 29, 2007, respectively) from the International Space Station. The pair documents the breakup of the Lake Erie ice pack, the unofficial signature of spring for residents of Buffalo and Niagara Falls. In March, the eastern end of Lake Erie is clogged with ice that is pushed against the shoreline by the prevailing westerly wind. The ice collects in Lake Erie, and the Lake Erie-Niagara River Ice Boom prevents it from flowing down the Niagara River, which is the international boundary between the Canadian Province of Ontario, and New York State. The 2,680-meter (8,800-foot) boom is deployed each December. Operational since 1964, the boom serves several functions: it protects the water intakes for the Niagara River power plants, and it minimizes ice runs (large blocks of ice flowing downstream as ice breaks up in the spring) and blockages that can create damage and flooding along the river. At the height of winter, the thickness of the ice at the Buffalo harbor can reach 3.5 meters (12 feet). The removal of the ice boom, usually in early April, is now marked by local celebrations. This year the boom was removed in mid-April, a bit later than usual. A webcam allows remote viewers to monitor ice pack at the boom. During their missions, astronauts track the changing seasons using such indicators as the springtime melting of ice packs in high-latitude oceans and lakes. Over the next two years, the space station astronauts will make these types of observations to support International Polar Year (IPY) investigations. Scientists interested in requesting high-latitude imagery from the space station for IPY science should visit the Johnson Space Center Gateway to Astronaut Photography of the Earth International Polar Year Website.
ISS015-E-7543	Concepcion Volcano, Nicaragua: Concepción Volcano one of the tallest and most active of Nicaragua’s volcanoes. The 1,610-meter (5,280-foot), cone-shaped volcano is the northern half of dumbbell-shaped Isla de Ometepe. Concepción is joined by a narrow isthmus to the dormant Maderas Volcano, which makes up the southern half of the island. This image of the volcano was captured on May 10, 2007, by the astronauts onboard the International Space Station. To the northwest of the crater, a very faint plume (probably steam) creeps like fog down the mountain, blurring the sharp gullies that carve the volcano’s flanks. The grid pattern of people’s fields surrounds the volcano, while lobes of forest line the lower slopes. Concepción has erupted at least 25 times in the past 125 years, but eruptions are not the only hazard for the 5,000 or so people who lives in small towns at lower elevations. Loose rock and ash from previous eruptions makes the volcano’s steep slopes unstable and prone to give way during heavy rains. These flows of muddy debris are known as lahars. Among the most serious lahars that have occurred at Concepción in recent years were those that occurred during the passage of Hurricane Mitch through the area in 1998. (Much more serious lahars occurred at Nicaragua’s Casita Volcano during Hurricane Mitch.) The gullies that can funnel debris quickly downslope into populated areas are obvious in the image. References and Related images: Lahar Hazards at Concepción Volcano, Nicaragua, a U.S. Geological Survey Webpage Wide-area view of western Nicaragua, including Lake Nicaragua and Isla Ometepe at lower right, from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite
ISS015-E-5977	Den Helder, Netherlands: The city and harbor of Den Helder in the northern Netherlands has been the home port of the Dutch Royal Navy for over 175 years. The location provides access to the North Sea, which has made it an important commercial and strategic port. Bright red agricultural fields to the south of Den Helder indicate another noteworthy aspect of the region—commercial farming of tulips and hyacinth. This astronaut photograph is an oblique view (an angled, not a “straight down”view) of the Den Helder region taken from the International Space Station (ISS). The ISS was located to the southeast, near Dülmen, Germany, when the image was acquired, about 225 kilometers (140 miles) away in terms of ground distance. In addition to the urban structures of the Den Helder area (reddish-gray to gray street grids) and dockyards to the east of the city, several striking natural features are visible. The prominent branching pattern of the extensive gray mudflats (image bottom right) indicate that this image was acquired at low tide, and show the generally low elevation of the region. Parallel wave patterns along the mudflats and in the Marsdiep Strait are formed as water interacts with the sea bottom between Den Helder and Texel Island during tidal flow. (Some ship wakes are also visible.) The bright, white-gray triangular region at the southern tip of Texel Island (image upper left) is a dune field, consisting mainly of eolian (wind-borne) sands deposited during the last ice age. Subsequent sea level rise and shoreline processes have shifted these sands into their current configuration, which includes a new dune field island to the southwest of Texel.
ISS015-E-8920	Southern Everglades National Park, Florida: Everglades National Park in southern Florida is the largest subtropical wilderness in the United States. Known as the “river of grass,” the Everglades wetlands and wooded uplands host a variety of endangered species including crocodiles, manatees, and panthers. During the late nineteenth and twentieth centuries, the original 11,000 square miles of wetlands were viewed as useless swampland in need of reclamation. The success of reclamation efforts—for agriculture and urban expansion in southern Florida—has led to the loss of approximately 50 percent of the original wetlands and 90 percent of wading bird species. Today, an extensive restoration effort is underway to return portions of the Everglades to a more natural state and prevent further ecosystem degradation. This astronaut photograph highlights the southern Everglades, where the wetlands meet Florida Bay. Thin fingers of land and small islands (keys) host mangrove, hardwood hammocks (tree-covered mounds), marsh and prairie (mainly dark to light green in the image). The tan and grayish-brown areas at image upper right are dominantly scrub, marshland and prairie; small green “dots” and narrow lines in this region are isolated mangrove and hardwood stands indicating the general direction of slow water flow toward the bay. The silver-gray regions at image left are water surfaces highlighted by sunglint, light reflected off the water surface directly back towards the astronaut aboard the International Space Station. The roadway forming the western boundary of the National Park is U.S. Route 1, which connects the Miami metropolitan area to the north (not shown) with the Florida Keys to the south (not shown). A small tan patch visible along the roadway is a fishing camp.
ISS015-E-10125	Iceberg A22A, South Atlantic Ocean: (image is paired with/compared to image ISS015-E-10118) This astronaut photograph illustrates the remains of a giant iceberg—designated A22A— that broke off Antarctica in 2002. The iceberg was photographed on May 30 at a location of 49.9 degrees south latitude, 23.8 degrees west longitude, which is about a third of the distance from South America towards Cape Town, South Africa. A22A is one of the largest icebergs to drift as far north as 50 degrees south latitude, bringing it beneath the daylight path of the International Space Station (ISS). Crew members aboard the ISS were able to locate the ice mass and photograph it, despite the great masses of clouds that often accompany winter storms in the Southern Ocean. The crew’s viewing angle was oblique (not looking straight down) from a point to the west of the berg, and the time of day was early afternoon, as shown by the orientation of the cloud shadows. Dimensions of A22A in early June were 49.9 by 23.4 kilometers, giving it an area of 622 square kilometers, or seven times the area of Manhattan Island. Images of the iceberg are being acquired from the ISS to support a study of massive icebergs—part of NASA International Polar Year activities. The study will increase understanding of the way ice sheets evolve as climate changes. When large masses of ice float into warmer waters north of their usual latitudes, they undergo change at rapidly increased rates. Changes that would take decades to occur in Antarctica can happen in a few years or even months in the warmer conditions at 50 degrees south latitude. The crew of the ISS will continue to collect imagery of the accelerating breakup of iceberg A22A as weather, orbital, and illumination conditions allow. More information, including Webcams, on the studies conducted on A22 and at other places in the Antarctic can be found at www.thistle.org and the National Snow and Ice Data Center’s Icetrek Website (http://nsidc.org/icetrek/).
ISS015-E-10704	Grey Glacier, Chile: The Southern Patagonian Icefield of Chile and Argentina hosts several spectacular glaciers—including Grey Glacier located in the Torres del Paine National Park in Chile. This glacier, which in 1996 had a measured total area of 270 square kilometers and a length of 28 kilometers (104 square miles in area, 17 miles long), begins in the Patagonian Andes Mountains to the west and terminates in three distinct lobes into Grey Lake (upper image). The upper image is a photograph taken by an astronaut aboard the International Space Station, and it captures a striking blue coloration of the glacier. The coloring is due to the ice’s absorption of red wavelengths of light and scattering of blue wavelengths of light as it is transmitted through the ice. Certain portions of the glacier visible in the image are indeed gray. Linear gray-brown moraines are accumulations of soil and rock debris that form along the edges of a glacier as it flows downhill across the landscape (much like a bulldozer blade). Glaciers flowing downslope through adjacent feeder valleys ultimately meet, and debris entrained along their sides becomes concentrated in the central portion of the resulting single, large glacier—much as smaller streams of water join to form a single large river. Three of these medial moraines are visible in the ice mass at image center left. Gray-brown patches of debris from adjacent mountainsides color the surface of the easternmost lobe of the glacier (image top). Several crevasse fields are visible in the image. The crevasses, each a small canyon in the ice, form as a result of stress between slower- and faster-moving ice within the glacier. The crevasse patterns of Grey Glacier are complex, perhaps due to the three-lobed nature of its terminus, or end, into Grey Lake. The rugged surface of the glacier is also demonstrated by the jagged shadows it casts onto the surface of the lake. The astronaut photograph, acquired in 2007, is compared with a false-color image from the Landsat 5 satellite captured in 1986. The false-color image highlights glacier ice in bright blue (lower image). Vegetation is bright green, and bare ground is pink. The general position of the glacier’s terminus in 2007 is marked with yellow lines on the 1986 image. All three lobes have retreated over the 22-year period, with the greatest loss of ice occurring along the westernmost lobe terminus. Grey Glacier, like others in southern Patagonia, loses ice from its terminus as it enters the water, a process known as calving. Calving produces large free-floating chunks of ice; some floating ice is visible near the central glacier lobe in the upper image. The observed retreat means that ice loss has been greater than ice replenishment. It is most likely due to a combination of increased regional temperatures and changes in precipitation amounts.
ISS015-E-5481	Patuxent River Naval Air Station, Maryland: Maryland’s Patuxent River Naval Air Station is located on a small peninsula, bordered by the Patuxent River to the north-northeast and Chesapeake Bay to the east and southeast. The air station was commissioned in 1943, replacing farmlands that had occupied the peninsula less than a year earlier. The primary purpose of “Pax River” (as the site is known by the U.S. Navy) was to consolidate geographically dispersed testing facilities that existed prior to World War II. The Patuxent River station is now the primary center for naval air technology research, development, testing, and support, as well as being the location of the Navy Test Pilot School. International Space Station crews frequently use the Patuxent River Naval Air Station as a geographic reference point and photographic training target. This astronaut photograph illustrates why—the distinctive pattern of the airfield runways and the station’s location in Chesapeake Bay make it easy to spot from orbit. The sharp boundaries between different kinds of land surfaces are good for camera focusing practice. This particular image also captures surface water current patterns around the peninsula. Wind- and wave-roughened water surfaces appear silver-gray due to increased reflectance of light back towards the camera (sunglint), whereas dark blue water patches indicate water smoothed by the presence of oils and surfactants (smooth water reflects less light back to the observer) from either natural or human sources. A zone of mixing from converging shoreline currents extends northeast into the bay from Cedar Point.
ISS015-E-5815	Algae in Great Salt Lake: The Great Salt Lake of northern Utah is a remnant of glacial Lake Bonneville that extended over much of present-day western Utah and into the neighboring states of Nevada and Idaho approximately 32,000 to 14,000 years ago. During this time, the peaks of adjacent ranges such as the Promontory and Lakeside Mountains were most likely islands. As climate warmed and precipitation decreased in the region, glaciers that fed meltwater to Lake Bonneville disappeared, and the lake began to dry up. The present-day Great Salt Lake is a terminal lake in that water does not flow out of the lake basin. Water loss through the year is due primarily to evaporation, and when this loss exceeds input of water from rivers, streams, precipitation, and groundwater, the lake level decreases. This is particularly evident during droughts. Evaporation and the relatively shallow water levels (maximum lake depth is around 33 feet), has led to increased salinity (dissolved salt content). The north arm of the lake, displayed in this astronaut photograph from April 30, 2007, typically has twice the salinity of the rest of the lake due to impoundment of water by a railroad causeway that crosses the lake from east to west. The causeway restricts water flow, and the separation has led to a striking division in the types of algae and bacteria found in the north and south arms of the lake. North of the causeway, the red algae Dunaliella salina and the bacterial species Halobacterium produce a pronounced reddish cast to the water, whereas south of the causeway, the water color is dominated by green algae such as Dunaliella viridis. The Great Salt Lake also supports brine shrimp and brine flies; and it is a major stopover point for migratory birds including avocets, stilts, and plovers.
ISS015-E-5983	Upheaval Dome, Utah: Upheaval Dome is a striking geologic structure in the Canyonlands National Park of southern Utah. Viewed from directly above (and on geologic maps), the alternating rock layers make a nearly circular, 5.5-kilometer- (3.4-mile-) diameter “bull’s-eye.” The oldest rocks are in the center (Chinle and Moenkopi Formations, with limited exposures of even older rocks), and progressively younger rocks are exposed farther out: Wingate Sandstone, Kayenta Formation, and Navajo Sandstone (in order of decreasing age). This kind of rock formation—a fold in the Earth’s crust in which the rocks slope downward from either side of a central point—is called an anticline. If the exposed rock layers form a closed circle at the surface, the anticline is called a dome. It is typical of these formations for the central rocks to be the oldest. This photograph of Upheaval Dome was taken by an astronaut onboard the International Space Station. The oblique viewing angle—in other words, not looking straight down—provides a sense of the topography within and around the structure. The dome appears more like an ellipse than a circle due to the oblique viewing perspective. Dark regions in the image are cloud and cliff shadows. Scientists propose at least two ideas about how Upheaval Dome formed. Some believe that the dome is a sign of a sub-surface salt dome—a rising plug of relatively low-density salt that caused overlying rock layers to dome up in a circular pattern like a basketball underneath a blanket. The overlying rock layers were uplifted and then eroded, leaving the bull’s-eye surface pattern. Another hypothesis identifies Upheaval Dome as an impact structure, caused by a meteor striking the Earth approximately 60 million years ago. In this interpretation, the erosion-resistant Navajo and Wingate Sandstones define multiple crater rings, while the Chinle, Moenkopi, and older rocks exposed in the middle of the dome are the central peak of the impact structure. Debate about the origin of Upheaval Dome continues; recent evidence—such as microscale deformations of the rocks and minerals that are consistent with a high-energy impact event—lends support to the impact-structure hypothesis.
ISS015-E-5483	Brooklyn, New York Waterfront: This astronaut photograph captures the dense urban fabric of Brooklyn, New York City’s largest borough (population of 2.6 million), characterized by the regular pattern of highly reflective building rooftops (white). Two main arteries from Manhattan into Brooklyn—the famous Brooklyn Bridge and neighboring Manhattan Bridge—cross the East River along the left (north) side of the image. The densely built-up landscape contrasts with the East River and Upper New York Bay (image lower right) waterfront areas, recognizable by docks and large industrial loading facilities that extend across the image center from left to right. Much of the shipping traffic has moved to the New Jersey side of New York Bay, a shift that has spurred dismantling and redevelopment of the historic dockyards and waterfront warehouses into residential properties. However, efforts to conserve historic buildings are also ongoing. The original name for Brooklyn, Breukelen, means “broken land” in Dutch, perhaps in recognition of the highly mixed deposits (boulders, sand, silt, and clay) left behind by the Wisconsin glacier between 20,000 and 90,000 years ago. These deposits form much of Long Island, of which Brooklyn occupies the western tip. This image features one of Brooklyn’s largest green spaces, the Green-Wood Cemetery. The green canopy of the cemetery’s trees contrasts sharply with the surrounding urban land cover. Today, the cemetery also functions as a natural park, and it is an Audubon Sanctuary. Also visible in the image is Governors Island, which served as a strategic military installation for the U.S. Army (1783–1966) and a major U.S. Coast Guard installation (1966–1996). Today the historic fortifications on the island and their surroundings comprise the Governors Island National Monument.

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