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At approximately five million years old, Bigach is a relatively young geologic feature. However, active tectonic processes in the region have caused movement of parts of the structure along faults, leading to a somewhat angular appearance (image center). The roughly circular rim of the 8-kilometer (diameter) structure is still discernable around the relatively flat interior.
In addition to modification by faulting and erosion, the interior of the impact structure has also been used for agricultural activities, as indicated by the presence of tan, graded fields. Other rectangular agricultural fields are visible to the northeast and east. The closest settlement, Novopavlovka, is barely visible near the top of the image.
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The brackish conditions (a mix of fresh and salt water) in most estuaries invite unique plant and animal species that are adapted to live in such environments. The hardy shrubs and trees of mangroves are common in and around Madagascar’s estuaries, and Bombetoka Bay contains some of the largest remaining stands. Estuaries also host abundant fish and shellfish species, many of which need access to fresh water for a portion of their life cycles. In turn, these species support local and migratory bird species that prey on them.
However, human activities such as urban development, overfishing, and increased sediment loading from erosion of upriver highlands threaten the health of the estuaries. In particular, the silt deposits in Bombetoka Bay at the mouth of the Betsiboka River have been filling in the bay.
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The dark-green forested floodplain is about 10 kilmeters (6 miles) wide where it enters the view (image left). The Okavango then enters a rift basin, which allows the river to spread out and form the wetland. The width of the rift determines the dimensions of the delta—150 kilometers (90 miles) from the apex to the downstream margin (image right). The apex fault is difficult to discern, but two fault lines define the downstream margin; the faults appear as linear stream channels and vegetation patterns oriented at right angles to the southeast-trending channels at image center.
The channels carry sediment from the Okavango River that is deposited within the rift basin. Over time, a fan-shaped morphology of deposits has developed, leading to characterization of the wetland as the Okavango “delta.”
The greens of denser savanna vegetation in the north give way to browns of the open “thornscrub” savanna to the south, matching the precipitation patterns of higher rainfall in the north and less rainfall in central Botswana. More subtle distinctions also appear: the arms of the delta include tall, permanent riverine forest and seasonal forest (dark green), with grasses and other savanna vegetation (light green) on floodplains.
Linear dunes, built up by constant winds from the east during drier climates, appear as straight lines at image left. The dunes are 10 meters high, and their sands hold enough moisture for some trees to grow on them. Counter-intuitively, the low “streets” between the dunes are treeless because they are dominated by dense, dry white soils known as calcretes.
Only 2 to 5 percent of the water that enters the Okavango delta flows out of it. (Compare the small Boteti River (image right), where water flows out of the delta, with the wide Okavango floodplain at image left.) In wetter years, some water reaches Lake Ngami (lower right), where it evaporates. Over the decades, various groups have argued that the 95 percent reduction in water from apex to toe of the delta is a “loss,” and that water from the Okavango might be better used for local, irrigated agriculture. Others have called for moving it via long canals to maintain the diamond mines to the south. Various cities also have proposed to use the water, including Pretoria (South Africa), Gaborone (Botswana), or Windhoek (Namibia).
Such plans have been vigorously fought by conservationists, who have argued that the water is critical for the pristine Okavango wetland. This protected wildlife zone attracts tourists from around the world.
Another feature in the image also suggests modern globalization. The curved line in the southwest part of the delta is the Southern Buffalo Fence, a major installation that separates wild buffalo herds within the wetland from cattle herds, which occupy more populated areas surrounding the delta (image bottom, image right). The fence divides lighter-toned and darker grassland; suggesting that vegetation growth is stronger (greener) on the populated southwest side than within the delta. The fence was erected to control the spread of foot-and-mouth disease from buffalo populations to the domestic cattle herds that are the basis of an expanding beef industry. Wildlife proponents argue that fences have affected the size of wild herds by disrupting migration routes. They also cause deaths by entanglement in the fence cables and by preventing animals from reaching water.
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This astronaut photograph highlights the nighttime appearance of the southern Italian Peninsula. The toe and heel of Italy’s “boot” are clearly defined by the lights of large cities such as Naples, Bari, and Brindisi, as well as numerous smaller cities and towns. The bordering Adriatic, Tyrrhenian, and Ionian Seas appear as dark regions to the east, west, and south. The city lights of Palermo and Catania, Sicily, are also visible.
The International Space Station (ISS) was located over an area of Romania, close to the capital city of Bucharest (approximately 945 kilometers to the northeast) at the time this image was taken. Part of a solar panel array on a docked Russian spacecraft is visible in the foreground. The distance between the image subject area and the position of the photographer, as well as the viewing angle looking outwards from the ISS, contributes to the foreshortened appearance of the Italian Peninsula and Sicily.
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The image is oriented with north on the left. The Sault Ste Marie urban areas (image lower left) have a distinctive gray to white color, contrasting with the deep green of forested areas in Ontario and the lighter green of agricultural fields in Michigan. The water surfaces in the lakes and rivers vary from blue to blue-green to silver, likely the result of varying degrees of sediment and sunglint—light reflecting from the water surface back to the International Space Station.
Prior to formalization of the US-Canada border in 1817, Sault Ste Marie was a single community. Archeological evidence suggests the region was occupied by Native Americans at least five hundred years ago. A mission—the first European settlement in Michigan—was established there in 1668 by the French Jesuit Father Jacques Marquette. Today, shipping locks and canals in both urban areas are an important part of the Great Lakes shipping traffic system.
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Several saline and ephemeral lakes—Nabberu, Teague, Shoemaker, and numerous smaller ponds—occupy the land surface between the ring structures. Differences in color result from both water depth and from suspended sediments, with some bright salt crusts visible around the edges of smaller ponds (image center). A Landsat 7 view of the Shoemaker structure illustrates the extent of these ephemeral lakes, or playas, in the region.
The Teague Impact Structure was renamed Shoemaker in honor of Dr. Eugene M. Shoemaker (1928-1997), a pioneer in impact crater studies and planetary geology, as well as the founder of the Astrogeology Branch of the U.S. Geological Survey.
Reference
Pirajno F., Hawke, P., Glikson, A.Y., Haines, P.W., and Uysal, T. (2003). Shoemaker impact structure, Western Australia. Australian Journal of Earth Sciences, 50:775-796.
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In the meantime, there is an actual mission going on, which you can follow here. In this astronaut photograph, the Space Shuttle Atlantis approaches the International Space Station for docking for the last time on July 10, 2011. Part of a Russian Progress spacecraft, also docked to the station, pokes into the upper foreground. Beneath them all lie the teal-colored shallows around the Bahamas.
It's easy to get caught up in the hardware and the engineering of the shuttle; and why not, it's a cool machine. But a lot of science has been conducted on that low-earth-orbiting observatory, much of it with the human eye. Here is a description from our latest tribute to shuttle science:
For all of the novel and sophisticated technology that has been flown on the space shuttles, the most underrated instrument to fly in space is the human eye.
“Humans are smart, trainable sensors,” says Kam Lulla, former chief scientist for Earth observation in the Human Exploration Science Office at NASA’s Johnson Space Center. Astronauts have unique sensing capabilities, including the knowledge to identify and interpret changes and features on the planet, and the ability to react to events and conditions—from changing the angle, width, or focus of a camera shot to adjusting for sunlight. “We take NASA’s astronauts, who are already very smart, accomplished people, and we work to make them Earth-smart. We train their minds for science in orbit.”
For most of the Space Shuttle program, each crew was trained to visually recognize 25 to 50 locations of interest to the Earth science community. Sometimes natural events added to the target list. Sometimes the astronaut’s eyes found beauty and surprises below.
“Photographs from the Space Shuttle are punctuated snapshots of distinct places on Earth,” says Cindy Evans, an Earth scientist and long-time trainer and ground-based guide to astronauts. “They are framed by a human eye and perspective, and they are accessible to anyone. These images speak to people. ”
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Atlantis is scheduled to land at Kennedy Space Center at 5:56 a.m. local time on July 21, concluding NASA’s 30-year space shuttle program. In addition to the science the shuttle and earlier programs enabled, human space flight has given us a unique view of planet Earth, which includes the now iconic spectacle of Earth rising over the Moon taken during the first lunar landing on July 20, 1969, and the photographs taken from Atlantis during its last full day in space on July 20, 2011. In fact every flight is a mission to planet Earth, as described in the Earth Observatory’s tribute to the shuttle program.
Observing Earth from space is one of the NASA’s longest-standing science experiments. Astronauts have used handheld cameras to photograph the Earth since the Mercury missions in the early 1960s, taking more than 800,000 photographs of Earth. Half of that total has come from the 135 flights of the Space Shuttle program.
“Astronauts are like tourists going to an exotic place, and we know they are going to take photos,” said Kam Lulla. “Early in the space program, NASA decided that if they were going to do this anyway, let’s get some science content out of it.” That was a wise decision.
Astronauts are still being trained for the view from space. The Space Shuttle program is ending, but the International Space Station offers its own vantage point of the planet—and astronauts will still be heading there for another decade.
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The dominant geographic feature in the region is Mt. Ararat, also known as Agri Dagi. The peak of Ararat, a large stratovolcano that last erupted in 1840 according to historical records, is located approximately 40 kilometers (25 miles) to the south of the Armenia-Turkey border. A lower peak to the east, known as Lesser or Little Ararat, is also volcanic in origin. Dark gray lava flows to the south of Mt. Ararat are located near the Turkish border with Iran. While this border is also closed along much of its length, official crossing points allow relatively easy travel between the two countries.
The white, glacier-clad peak of Mt. Ararat is evident at image center; dark green areas on the lower slopes indicate where vegetation cover is abundant. A large lake, Balik Golu or Fish Lake, is visible to the west (image lower left).
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At the time of the image, the ISS was positioned northwest of the Galapagos Islands, while Atlantis was roughly 2,200 kilometers (1,367 miles) to the northeast, off the east coast of the Yucatan Peninsula. The maximum angle of the shuttle’s descent was roughly 20 degrees, though it appears much steeper in the photo because of the oblique viewing angle from ISS. Parts of the space station are visible in the upper right corner of the image.
In the background of the image, airglow hovers over the limb of the Earth. Airglow occurs as atoms and molecules high in the atmosphere (above 80 kilometers, or 50 miles altitude) release energy at night after being excited by sunlight (particularly ultraviolet) during the day. Much of the green glow can be attributed to oxygen molecules.
Over the years, the space shuttle program has gathered many images and insights on earth’s space environment—including auroras—and on the planet below. We explore the role the shuttle has played in observing our home planet:
In the 1980s and early 1990s, NASA embraced a “systems” approach to studying Earth science. Where land- and ocean-based scientists could make observations in great depth from individual points, space-based sensors could examine entire regimes of Earth with a broader but shallower view—the global ocean surface, plant cover over all continents, the composition of the atmosphere both horizontally and vertically. Scientists could ultimately piece together the micro and macro scales for a deeper understanding of how the planet works.
Equipped with a 60-foot-long payload bay, a nimble robotic arm, and two to seven pairs of human hands and eyes (depending on the size of the crew), the Space Shuttle became an orbiting laboratory and observatory for Earth system science. The shuttle could not observe continuously for months to years, as satellites might. But the human touch and the frequent flights did allow some intensive and diverse studies.
Over three decades, the shuttle served as a critical testbed for remote sensing instruments that would eventually fly on satellites. In fact, many of the technologies in NASA’s Earth Observing System made their maiden flights in the back of NASA’s space pick-up truck.
