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Earth from Space – Crepuscular rays

Crepuscular rays seen from space

Rays of light and dark appear to emanate from clouds in this image taken by an astronaut aboard the International Space Station. They are called crepuscular rays.

CREPUSCULAR RAYS OVER THE OCEAN near India are featured in this image photographed by an Expedition 29 crewmember on the International Space Station.

The sight of shafts of light, beaming down from the heavens through a layer of clouds, has provided many an artist, scientist, and philosopher with inspiration throughout the centuries.

Atmospheric scientists refer to this phenomenon as “crepuscular rays“, referring to the typical observation times of either sunrise or sunset.

Shadowed areas bounding the rays are formed by obstructions in the solar (or lunar) illumination pathway such as clouds or mountaintops; however this alone is not sufficient to create the phenomenon. The light must also be scattered—by airborne dust, aerosols, water droplets, or molecules of the air itself—to provide the visible contrast between the shadowed and illuminated parts of the sky.

Crepuscular rays seen from the ground.

A ground-based image of crepuscular rays shows them appear to radiate from a central point, a perspective effect. The orbital image above shows them in fact to be parallel.

When observed from the ground, crepuscular rays appear to radiate outwards from the source of illumination due to the effects of distance and perspective; however the rays are actually parallel.

This photograph from the Space Station provides an unusual viewing perspective from above the rays. The sun was setting to the west on the Indian subcontinent at the time the image was taken, and cumulonimbus cloud towers provide the shadowing obstructions.

The rays are being projected onto a layer of haze below the cloud towers. The image clearly illustrates the true parallel nature of the crepuscular rays.

See the full-size image here.

Orbital image courtesy NASA. Ground-based image of crepuscular rays from Wikipedia, courtesy Chevy111, posted under the Creative Commons Attribution-ShareAlike 3.0 License.

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Earth from Space – Rowley Shoals

ISS photo of Rowley Shoals

Rowley Shoals in the Timor Sea, as photographed by an astronaut aboard the International Space Station.

THIS PHOTOGRAPH—taken by an Expedition 29 crewmember on the International Space Station—highlights the trio of coral reef atolls known as Rowley Shoals, located in the southwestern Timor Sea.

Three reef areas make up the shoals—extending approximately 100 kilometres from northeast to southwest, they are Mermaid Reef, Clerke Reef, and Imperieuse Reef.

Only Clerke Reef and Imperieuse Reef have white sandy islets (or cays) that remain above water. Imperieuse Reef also has the only permanent man-made structure–a lighthouse located on Cunningham Islet, a cay at the northern end of the reef.

Thin patchy cloud cover also is visible.

Close-up of Imperieuse Reef

Close-up of Imperieuse Reef

Rowley Shoals is located off the northwestern Australia coastline, approximately 300 kilometres west of the city of Broome. Since the late 1970s, fishing and diving expeditions—based in Broome—have frequented the atolls of the Shoals.

Clerke and Imperieuse Reefs are part of the Rowley Shoals Marine Park established in 1990. Mermaid Reef is also managed as the Mermaid Reef Marine National Nature Reserve (established in 1991).

The biodiversity of the atolls is impressive, with 233 coral species and 688 fish species more typical of Southeast Asia than other Western Australian reef ecosystems. Species include staghorn coral, giant clams, giant potato cod, maori wrasse, mackerel and tuna.

In addition, Bedwell Island (a cay in Clerke Reef) hosts a colony of red-tailed tropicbirds as well as species of shearwaters, sea-eagles, terns, plovers and egrets.

See the full-size image here.

Adapted from information issued by NASA.

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Earth from Space – Night turns to day

The Mediterranean region at night

The Mediterranean region, illuminated by manmade lights and natural sources (moonlight, starlight etc).

ONE OF THE EXPEDITION 29 crewmembers aboard the International Space Station took this oblique angle photo showing the Mediterranean Sea area, including the Nile River and the river’s delta, and the Sinai Peninsula, on October 15, 2011. Cyprus is visible at left.

At first look, the image appears to have been photographed in daylight, but actually it was taken in the early hours of the morning, local time.

Some areas of the photo like the river and river delta appear as the brightest areas because of either man-made lighting (mostly incandescent) or man-made lighting reflected off nearby surfaces.

The rest of the region is illuminated naturally by moonlight, starlight, or back-scattered light from the atmosphere.

Also visible is a green band following the curve of the horizon. This is airglow.

Below is another, slightly wider view.

Download full-size, high-resolution versions of the images:

Image 1

Image 2

The Mediterranean region at night

A wider view photographed at roughly the same time.

Adapted from information issued by NASA.

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Earth from Space – Videos of our World

TAKE A LOOK AT THESE VIDEOS of our amazing planet. The footage was shot from the International Space Station, orbiting hundreds of kilometres above our head.

The videos are only short, and in some cases speeded up; nevertheless they give an incredible “astronauts’ eye view” of what various parts of our planet look like from space.

Story by Jonathan Nally. Videos courtesy NASA.

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Earth from Space – Petermann Ice Island

Petermann Ice Island seen from space

The huge Petermann Ice Island broke free from Greenland's Petermann Glacier in August 2010.

AFTER  MORE THAN A YEAR and several thousand kilometres of sailing the seas, Petermann Ice Island is still drifting in the North Atlantic off the shores of Newfoundland, Canada.

Once a hunk of ice fives times the size of Manhattan Island, the ice island has splintered several times since it dropped off the edge of Greenland’s Petermann Glacier.

Yet still it behaves a bit like the massive ice sheet it left 14 months ago.

Astronauts on the International Space Station used a digital camera to capture this view of Petermann Ice Island A, fragment 2, off of the northeast coast of Newfoundland on August 29, 2011.

Spanning roughly 4 kilometres by 3.5 kilometres, the ice island is covered with melt ponds and streams, much as the surface of Greenland looks in mid-summer.

As ice melts on top of the Greenland ice sheet, the melt water forms streams and pools in the depressions on the ice surface. Drawn downslope by gravity—much like streams on a mountainside—water also runs toward the edges of the ice. In some cases, it cracks through it and rushes to the bottom.

Such processes appear to be at work on the ice island as well.

August 2011 was a busy month in the life of the ice island, according to the Canadian Ice Service. On August 7, it became grounded on a shoal or shallow seafloor off of St. Anthony, Newfoundland, where it sat for 11 days.

By August 18, the ice island broke free and began drifting again, only to split into two large pieces about five days later. The Ice Service last reported on it on August 25.

See the full-size image of the Petermann Ice Island here.

Astronaut photograph provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text adapted from information issued by Mike Carlowicz.

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Earth from Space – Roze Glacier

Satellite image of Roze Glacier

Russia's remote Severny Island is home to the huge Roze Glacier.

PART OF THE RUSSIAN FEDERATION, the archipelago of Novaya Zemlya consists of two big islands—Yuzhny in the southwest, and Severny in the northeast—separated by a narrow strait. The archipelago divides the Barents Sea from the Kara Sea.

An ice cap covers much of Severny, and from this ice cap, several outlet glaciers flow seaward. The easternmost glacier on Severny’s southeastern coast is Roze.

On June 5, 2011, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-colour image of Roze Glacier fringed by sea ice.

The glacier pushes slowly seaward between two rocky ridges. Uneven snow cover on the rock surfaces creates a patchwork of brown and white. Some snow also rests on the adjacent sea ice, which appears in shades of white and gray. In the east, a large patch of gray ice immediately offshore may owe its colour to a layer of melt water or simply a lack of snow cover.

On the glacier itself, isolated pools of melt water form ovals and slivers of blue-gray. Dwarfing the melt ponds, two long parallel stripes extend southward toward the coast. The stripes look like debris along the sides of a relatively fast-flowing ice stream, which may have picked up rocks and dirt from an upslope rock outcrop.

Glaciers gain ice through snow accumulation, and lose it through melting and calving icebergs. A report released in 2006 by the Laboratoire d’Etudes en Géophysique et Océanographie Spatiales stated that Roze Glacier, in addition to other glaciers along Severny’s southeastern coast, underwent overall ice loss between 1990 and 2000.

Several hundred years ago, the Little Ice Age prompted many glaciers to advance. Glaciers do not respond to changing climate immediately, but may advance or retreat years, decades, even centuries afterwards.

A study published in 2009 reported that the glaciers on Novaya Zemlya likely reached their maximum extent related to the Little Ice Age near the end of the nineteenth century, and have since retreated at varying rates.

See the full-size image of Roze Glacier here.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Text adapted from information issued by Michon Scott based on image interpretation by Walt Meier, National Snow and Ice Data Centre.

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Earth from Space – Sand dunes

Dunes in the Burqin-Haba River-Jimunai Desert

Huge dunes dot the Burqin-Haba River-Jimunai Desert near the borders of China, Mongolia, Russia and Kazakhstan.

A SAND DUNE FIELD within the Burqin-Haba River-Jimunai Desert near the borders of China, Mongolia, Russia and Kazakhstan, is seen in this photograph taken by an astronaut on the International Space Station.

The dune field (approximately 32 kilometres long) is located immediately west-northwest of the city of Burqin (not shown), and is part of the Junggar Basin, a region of active petroleum production in northwestern China.

The Irtysh River—with associated wetlands and riparian vegetation (appearing grey-green in the image) —flows from its headwaters in the Altay Mountains towards Siberia (right to left across the image).

Tan, linear dunes at image centre (on the south side of the Irtysh River) dominate the view. The dunes are formed from mobile barchan (crescent-shaped) dunes moving from left to right in this view. The barchans eventually merge to form the large, linear dunes, which can reach 50 to 100 metres in height.

Sand moving along the southern edge of the field appears to be feeding a southeastern lobe with a separate population of linear dunes (image lower right).

The Burqin-Haba River-Jimunai Desert area also includes darker gravel-covered surfaces that form pavements known locally as gobi. At the resolution of an astronaut photograph, these are somewhat indistinguishable from the vegetated areas arresting some of the dunes. But gobi tend to be located on the flat regions between the dunes.

See the full-size image of the Burqin-Haba River-Jimunai Desert dunes.

Astronaut photograph provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text adapted from information issued by William L. Stefanov and M. Justin Wilkinson, Jacobs/ESCG at NASA-JSC.

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Earth from Space – Åland Islands

Landsat 7 image of the Åland Islands

The Åland Islands lie between Sweden and Finland.

THE ÅLAND ISLANDS (also known as the Aaland Islands) lie at the southern end of the Gulf of Bothnia, between Sweden and Finland. The archipelago consists of several large islands and roughly 6,500 small isles, many of them too small for human habitation.

Åland vegetation is a combination of pine and deciduous forest, meadows, and farmed fields. On nearly every island, however, the region’s characteristic red rapakivi granite appears.

Modern residents of Åland cut and use the granite in buildings and pavement, but much earlier, ice sculpted these rocks. About 20,000 years ago, a massive ice sheet stretched over Scandinavia and the Gulf of Bothnia, and glacial action gradually wore the granite smooth.

The granite in this region is actually far older than the glaciers that smoothed its surface, having formed in the Proterozoic Era. The rapakivi was deposited tens of millions of years before the first amphibians crawled out of water and onto land, and hundreds of millions of years before the first dinosaurs evolved.

NASA Earth Observatory Landsat 7 image created by Jesse Allen and Robert Simmon, using Landsat data provided by the United States Geological Survey. Text adapted from information issued by Michon Scott.

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Rare view of Earth and Moon

Juno spacecraft image of Earth and Moon

Earth and Moon, as seen by the Juno spacecraft from a distance of around 10 million kilometres

LOOKING HOMEWARD in its long journey to Jupiter, NASA’s Juno spacecraft offered up this rare view of our home planet with its moon. The spacecraft was nearly 10 million kilometres from Earth when it took this photo on August 26, 2011.

From that distance, oceans, land, clouds, and ice blend into a blur of light, a mere dot against the vastness of space. Even fainter and smaller, the Moon provides an additional sense of scale—the Earth and Moon are about 402,000 kilometres apart. (Juno travelled the Earth–Moon distance in less than a day.)

The spacecraft launched on August 5, and will reach Jupiter, another 2,800 million kilometres away, in about five years. The mission team took the photo as part of the first detailed check of the spacecraft’s instruments and subsystems.

“This is a remarkable sight people get to see all too rarely,” said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio, in a NASA release.

“This view of our planet shows how Earth looks from the outside, illustrating a special perspective of our role and place in the universe. We see a humbling yet beautiful view of ourselves.”

Adapted from information issued by NASA/JPL-Caltech and Holli Riebeek / NASA Earth Observatory.

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Seeing Earth’s night-lights

Orbital night-time view of southern California, Mexico's Baja California and the Gulf of Cortez

City lights illuminate this night time view of southern California, Mexico's Baja California and the Gulf of Cortez, as photographed by one the Expedition 28 crew members onboard the International Space Station flying at altitude of approximately 220 miles. The Salton Sea can be seen in the lower right quadrant of the frame. A solar panel and part of one of the space station's modules are silhouetted at right. A 15-mm focal length was used to capture the time-lapse image. The thin line of Earth's atmosphere is visible above the horizon.

IN ONE SENSE IT LOOKS PRETTY, but in another it reveals enormous and callous waste. Poorly designed and implemented lighting results in a lot of light being sent straight up into space, instead of down onto the ground where most of it is supposed to go.

This waste light consumes enormous amounts of energy, which ordinary citizens are paying for.

Not only that, but this upward-directed light also bounces around in the air, making the sky glow in a phenomenon astronomers call “light pollution“.

Comparison of light-polluted and non-light polluted skies.

The combined image shows how light pollution affects the appearance of clouds at night. The photo at left, taken by Ray Stinson in Glacier National Park, shows that in pristine areas clouds appear black, because they block out starlight. The photo at right, taken by Christopher Kyba in Berlin, was published as a part of a light pollution research paper, and shows how clouds are lit from below by light pollution, dramatically brightening the night sky. Photo courtesy Ray Stinson and Christopher Kyba, used under the Creative Commons Attribution-Share Alike 3.0 Unported licence.

Light pollution is a major problem, not just for astronomers—who find that many of the faint astronomical objects they want to see are “drowned out” by sky glow—but also for the environment. Wasted energy means more power-generated pollution than there needs to be, and waste light also can affect animal and plant life.

A lot of good work has been done in recent decades to begin correcting this problem, but there is still a long way to go.

As ideal illustrations of the scale of the problem, shown below are some recent nighttime photos taken by astronauts aboard the International Space Station.

More information:

Light pollution

International Dark Sky Association

Orbital nighttime view of the Nile River and the Sinai Peninsula

The Nile River and the Sinai Peninsula can be easily delineated in this nighttime photo captured by one of the Expedition 28 crewmembers aboard the International Space Station, flying at an altitude of approximately 220 miles. A 42-mm focal length was used to record the image.

Orbital nighttime view of the Nile River Delta and part of the Mediterranean Sea

The Nile River Delta and part of the Mediterranean Sea can be seen in this night time photo captured by one of the Expedition 28 crew members aboard the International Space Station, flying at an altitude of approximately 220 miles. A 38-mm focal length was used to record the image.

Orbital nighttime view of Sicily

Sicily is featured in this nighttime image captured by one of the Expedition 28 crewmembers aboard the International Space Station, approximately 220 miles above Earth. The landmass at left edge is part of the "toe" of Italy's "boot." A 38-mm lens was used to record the image.

Orbital nighttime view of the "boot" of Italy

The "boot" of Italy is featured in this nighttime image photographed by one of the Expedition 28 crewmembers aboard the International Space Station. A tip of Sicily is at top centre of the frame, photographed from approximately 220 miles above Earth. A 35-mm lens was used to record the image.

Orbital nighttime view of northwestern Europe

This nighttime view of northwestern Europe is featured in this image photographed by an Expedition 28 crewmember on the International Space Station. Several of the oldest cities of northwestern Europe are highlighted in this photograph taken at 00:25:26 Greenwich Mean Time (GMT). While the landscape is dotted with numerous clusters of lights from individual urban areas, the metropolitan areas of London (United Kingdom), Paris (France), Brussels (Belgium) and Amsterdam (Netherlands) stand out due to their large light "footprints". The metropolitan area of Milan, Italy is also visible at lower left. This photograph was taken with a short camera lens, providing the large field of view recorded in the image. To give a sense of scale, the centres of the London and Paris metropolitan areas are approximately 340 kilometres distant from each other. The image is also oblique, or taken while looking outward at an angle from the station; this tends to foreshorten the image, making the distance between Paris and Milan (approximately 640 kilometres) appear less than that of Paris to London. In contrast to the land surface defined by the city lights, the English Channel at right presents a uniform dark appearance. Similarly, the Alps (bottom centre) to the north of Milan are also largely devoid of lights. While much of the atmosphere was clear at the time the image was taken, the lights of the Brussels metropolitan area are dimmed by thin cloud cover.

Story by Jonathan Nally, SpaceInfo.com.au. Orbital images and captions courtesy NASA.

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