Jebel Uweinat (1,934 meters, mountain of sourcelets) is a mountain range in the area of the Egyptian-Sudanese-Libyan border. In general, the west slope constitutes an oasis, with wells, bushes and grass. The area is notable for its prehistoric petroglyphs. Engraved in sandstone, petroglyphs of Bushmen style are visible, representing giraffes, lions, ostriches, gazelles, and human figures. The western part of the massive consists of intrusive granite, arranged in a ring shape of some 25 km diameter. Its eastern part consists of sandstone; four plateaus emerge from the level of the surrounding desert. One of the driest places on earth, it reportedly hasn't rained since 1998 (Wikipedia). The image was acquired March 17, 2012, covers an area of 40 x 43 km, and is located at 22 degrees north latitude, 24.9 degrees east longitude.
Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
CryoSat altimeter view of sea level and topography over the Caribbean Sea and Cuba. The image shows radar reflections that differ in intensity between the water and elevated land. Near the edges of the island, points of high radar reflections are pictured in red. This is due to the higher reflectiveness of calm waters of the bay and over coral reefs.
Image credit: ESA
The Kangerdlugssuaq glacier and its ice stream are pictured in this week’s image, acquired on 19 September 2012 by Landsat-7. It is the largest outlet glacier on Greenland’s east coast, discharging ice into the surrounding oceans. In this image we can see hundreds of icebergs speckling the water. A recent study based on satellite observations revealed that over the past 20 years the ice melting in Greenland and Antarctica has contributed about 11 mm to the global sea-level rise. This image clearly shows the glacier’s calving front, where ice breaks away. Over the years, satellite images have shown that this front has retreated – an indication that the glacier is getting smaller over time.
This image is featured on the Earth from Space video program.
Photo credit: USGS/ESA
This image is a compilation of three radar images from the Japanese ALOS satellite and shows the Po River, which flows over 650 km from west to east across northern Italy as the country’s longest river. Agriculture is one of the main economic uses of the Po Basin because of the fertile soils, and this image clearly shows a landscape dominated by fields. Branching off of the river in the center of the image and snaking through the landscape to the lower-right corner is the Po di Goro, one of the main channels of the Po Delta. The section of the main river pictured and the Po di Goro form the border of the Italy’s Veneto (north) and Emilia–Romagna (south) regions.
This image is featured on the Earth from Space video program.
Image credit: JAXA/ESA
The Proba-1 microsatellite's High Resolution Camera images the French-Italian Concordia base in the Antarctic interior. The image has 5-m spatial resolution and covers approximately 25 sq km. It was acquired on 24 November 2012.
Photo credit: ESA
This Envisat image shows West Africa around the Gulf of Guinea, with parts of Nigeria to the north and Cameroon to the east visible. Cameroon’s largest city of Douala is located near the Wouri estuary near the center of the image. North of the Wouri estuary, the Mount Cameroon volcano is clearly visible. The island of Bioko is pictured just off the coast.
Reflections of Envisat’s radar signal appear like specks of white throughout the image. They are particularly concentrated around cities such as Malabo on the island, Douala near the Wouri estuary and the populated areas of southern Nigeria. These white specks are the typical appearance of built-up areas in radar images, owing to the multiple reflection of the radar beam by buildings and especially metal constructions.
This image is a compilation of three images from Envisat’s radar, acquired on 6 February, 7 March and 6 April 2012 – just two days before communication with the satellite was lost.
Image credit: ESA
Model of vertical movement across Santorini from January 2011 to present, derived from data from the Envisat and TerraSAR-X missions. Over the past year and a half, parts of Santorini have risen by 14 cm, such as the Kameni islands in the center. Scientists believe that new molten rock has been squeezing up beneath the volcano at a depth of about 4 km, pictured here as a red dot.
Image credit: M. Parks
This ALOS satellite image shows an area with extensive agricultural use in western Russia, with roads and rivers cutting through the cropland. This area, part of Russia’s Black Earth Region, is about 400 km directly south of Moscow. Many grains are grown here, such as winter wheat and rye.
This image is a compilation of three passes by the Japanese Advanced Land Observation Satellite’s radar on 14 June 2009, 14 September 2009 and 2 August 2010. Each image at the different recording date is assigned a color (red, green or blue) and combined to produce this representation. The colors reveal changes in the surface between the satellite’s passes.
Photo credit: JAXA, ESA
As the U.S. Midwest continues to suffer from near-historic drought conditions, farmers in southwestern Kansas are among the hardest hit. According to the U.S. Department of Agriculture, the area is under "exceptional drought" conditions. This has led to significant reductions of the corn, soybean and pea crops. The two satellite images shown here, obtained about 10 years apart, clearly illustrate the effects of the drought. The top half of this image was acquired on September 6, 2012 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft; the bottom half of the image was acquired by the Landsat Thematic Mapper on September 15, 2002. Vegetation appears in red, and bare fields are gray or greenish in color. Both images cover an area of 9.3 by 27.9 miles (15 by 44.5 kilometers) and are located near 38.2 degrees north latitude, 100.8 degrees west longitude.
Image credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
This animation shows Arctic ice cover from 1978 to 2010. The past five years have seen the lowest Arctic sea-ice extent since satellite measurements began in the 1970s.
Video credit: ESA/DLR
Anyone who's ever seen a noctilucent cloud or “NLC” would agree: They look alien. The electric-blue ripples and pale tendrils of NLCs reaching across the night sky resemble something from another world.
Researchers say that's not far off. A key ingredient for the mysterious clouds comes from outer space.
"We've detected bits of 'meteor smoke' embedded in noctilucent clouds," reports James Russell of Hampton University, principal investigator of NASA's AIM mission to study the phenomenon. "This discovery supports the theory that meteor dust is the nucleating agent around which NLCs form."
Noctilucent clouds are a mystery dating back to the late 19th century. Northern sky watchers first noticed them in 1885 about two years after the eruption of Krakatoa. Ash from the Indonesian volcano caused such splendid sunsets that evening sky watching became a worldwide pastime. One observer in particular, a German named T.W. Backhouse who is often credited with the discovery of NLCs, noticed something odd. He stayed outside longer than most people, long enough for the twilight to fully darken, and on some nights he saw wispy filaments glowing electric blue against the black sky. Scientists of the day figured they were some manifestation of volcanic dust.
Eventually Krakatoa’s ash settled and the sunsets faded, but strangely the noctilucent clouds didn’t go away. They’re still present today, stronger than ever. Researchers aren’t sure what role Krakatoa’s ash played in those early sightings. One thing is clear, however: The dust behind the clouds we see now is space dust.
Mark Hervig of the company GATS, Inc, led the team that found the extraterrestrial connection.
"Using AIM's Solar Occultation for Ice Experiment (SOFIE), we found that about 3% of each ice crystal in a noctilucent cloud is meteoritic," says Hervig.
The inner solar system is littered with meteoroids of all shapes and sizes--from asteroid-sized chunks of rock to microscopic specks of dust. Every day Earth scoops up tons of the material, mostly the small stuff. When meteoroids hit our atmosphere and burn up, they leave behind a haze of tiny particles suspended 70 km to 100 km above Earth's surface.
It's no coincidence that NLCs form 83 km high, squarely inside the meteor smoke zone.
Specks of meteor smoke act as gathering points where water molecules can assemble themselves into ice crystals. The process is called "nucleation."
Nucleation happens all the time in the lower atmosphere. In ordinary clouds, airborne specks of dust and even living microbes can serve as nucleation sites. Tiny ice crystals, drops of water, and snowflakes grow around these particles, falling to Earth if and when they become heavy enough.
Nucleating agents are especially important in the ethereal realm of NLCs. The clouds form at the edge of space where the air pressure is little more than vacuum. The odds of two water molecules meeting is slim, and of sticking together slimmer still.
Meteor smoke helps beat the odds. According AIM data, ice crystals can grow around meteoritic dust to sizes ranging from 20 to 70 nanometers. For comparison, cirrus clouds in the lower atmosphere where water is abundant contain crystals 10 to 100 times larger.
The small size of the ice crystals explains the clouds' blue color. Small particles tend to scatter short wavelengths of light (blue) more strongly than long wavelengths (red). So when a beam of sunlight hits an NLC, blue is the color that gets scattered down to Earth.
Meteor smoke explains much about NLCs, but a key mystery remains: Why are the clouds brightening and spreading?
In the 19th century, NLCs were confined to high latitudes—places like Canada and Scandinavia. In recent times, however, they have been spotted as far south as Colorado, Utah and Nebraska. The reason, Russell believes, is climate change. One of the greenhouse gases that has become more abundant in Earth's atmosphere since the 19th century is methane. It comes from landfills, natural gas and petroleum systems, agricultural activities, and coal mining.
It turns out that methane boosts NLCs.
Russell explains: "When methane makes its way into the upper atmosphere, it is oxidized by a complex series of reactions to form water vapor. This extra water vapor is then available to grow ice crystals for NLCs."
If this idea is correct, noctilucent clouds are a sort of "canary in a coal mine" for one of the most important greenhouse gases.
And that, says Russell, is a great reason to study them. "Noctilucent clouds might look alien, but they're telling us something very important about our own planet."
Photo credit: NASA;
video credit: NASA
Preparations for London's 2012 Summer Olympic Games began years before July 27th's opening ceremonies. The Games use a mixture of new venues, existing and historical facilities, and temporary facilities. Major construction projects included the new 400-acre Olympic Park, constructed on a former industrial site in the east of London.
This simulated natural color image of London was acquired May 26, 2012, by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft. It covers an area measuring 9.3 by 9.3 miles (15 by 15 kilometers), and is centered at 51.5 degrees North Latitude, 0.1 degree west longitude. The Olympic Park is visible in the upper right of the image.
Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
This animation shows deforestation of the Amazon Rainforest in the western Brazilian state of Rondônia from 1986 to 2010. While the central area remains green and untouched, squares of light green and brown pop up over time as the forest is cut away.
The animation was created using two cloud-free images: the first from NASA’s Landsat mission in 1986, and the second from the Spanish Deimos mission in 2010. The changes over time were simulated by referring to other satellite data acquired during the 24 years between the two images.
Video credit: ESA/USGS/Deimos Imaging;
text credit: ESA/USGS/Deimos Imaging
The Petermann Glacier grinds and slides toward the sea along the northwestern coast of Greenland, terminating in a giant floating ice tongue. Like other glaciers that end in the ocean, Petermann periodically calves icebergs. A massive iceberg, or ice island, broke off of the Petermann Glacier in 2010. Now, nearly two years later, another chunk of ice has broken free.
The Moderate Resolution Imaging Spectroradiometer, or MODIS, on NASA’s Aqua satellite observed the new iceberg calving and drifting downstream on July 16–17, 2012. Because Aqua is a polar-orbiting satellite, it makes multiple passes over the polar regions each day.
Photo credit: NASA
This image from ALOS shows southern France and the divide of the Rhone River: the 'Grand Rhône' flows down the center of the image while the 'Petit Rhône' is visible to the west. This divide at the French city of Arles forms the Camargue delta region. In the upper right corner of the image, we can see the Alpilles mountains. The green area south of the mountains is a large nature reserve.
This image is a compilation of three radar passes on 14 May 2008, 20 May 2010 and 5 July 2010. Each is assigned a color (red, green or blue) and combined to produce this representation. The colors reveal changes in the surface between the satellite’s passes.
Photo credit: JAXA, ESA
Tapping into fossil ground water, Saudi Arabia has been steadily developing agricultural fields using center pivot irrigation. A remarkable example is in the Wadi As-Sirhan Basin in northwest Saudi Arabia. In the 1984 Landsat image (top), no fields are yet present. By 2000, ASTER showed extensive farming activity (middle); vegetation is bright red. And by 2011, the ASTER image shows several areas where wall-to-wall fields were developed, each about 1 km in diameter (bottom). The images cover an area of 19.5 x 33 km, and are located at 30.5 degrees north latitude, 38 degrees east longitude.
Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
Dawson, Canada was a boom town in 1898, with a population of 40,000. Discovery of gold in the Klondike fueled the massive influx of miners, merchants, and other support professions to this town on the Yukon River. The current population is just over 1,000, with over 60,000 tourists invading the town each summer. Shortly after gold discovery, large gold dredges began an industrial mining operation, leaving large tailings piles in their wake. These can be clearly seen along the creek east of Dawson. The image was acquired September 19, 2010, and is located at 64.1 degrees north latitude, 136.4 degrees west longitude.
Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
The Waldo Canyon Fire, west of Colorado Springs, Colo., is being called the worst fire in Colorado history. Since its onset on June 23, 2012, the fire has consumed more than 18,000 acres and hundreds of homes. Containment of the fire is expected by July 6. In this image, acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft on July 4, healthy vegetation is red, water is dark blue, streets and buildings are gray, and the burned areas are black. The image covers an area of 9.3 by 12.1 miles (15 by 18 kilometers) and is located at 36.9 degrees north latitude, 104.9 degrees west longitude.
Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
This image acquired on 3 May 2012 from the Pleiades satellite shows the island of Mont Saint Michel and its surrounding bay in northwest France. Mont Saint Michel was a tidal island, meaning that it was surrounded by water at high tide and only when the waters receded was it reachable by foot. In the late 1800s, the causeway was raised to make it accessible from the mainland at all times. In this image, we can clearly see where the water meets the mud flats, with multiple channels weaving through the mud.
Photo credit: CNES 2012/Astrium Services/Spot Image
