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File NameFile Size (bytes)WidthHeightAnnotatedCroppedPurposeComments
View ISS031-E-30896.JPG 47813640425 No No
View ISS031-E-30896.JPG 237730540359 Yes Yes NASA's Earth Observatory web site
View ISS031-E-30896.JPG 6296151000664 No Yes NASA's Earth Observatory web site
View ISS031-E-30896.JPG 100718542882848 No No

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Mission: ISS031 Roll: E Frame: 30896 Mission ID on the Film or image: ISS031
Country or Geographic Name: KAZAKHSTAN
Center Point: Latitude: 44.9 Longitude: 53.7 (Negative numbers indicate south for latitude and west for longitude)

Stereo: (Yes indicates there is an adjacent picture of the same area)


Camera Tilt: 45
Camera Focal Length: 180mm
Camera: N2: Nikon D2Xs
Film: 4288E : 4288 x 2848 pixel CMOS sensor, RGBG imager color filter.


Film Exposure:
Percentage of Cloud Cover: 10 (0-10)


GMT Date: 20120511 (YYYYMMDD) GMT Time: 050638 (HHMMSS)
Nadir Point Latitude: 46.4, Longitude: 56.9 (Negative numbers indicate south for latitude and west for longitude)

Nadir to Photo Center Direction: West
Sun Azimuth: 112 (Clockwise angle in degrees from north to the sun measured at the nadir point)
Spacecraft Altitude: 214 nautical miles (396 km)
Sun Elevation Angle: 43 (Angle in degrees between the horizon and the sun, measured at the nadir point)
Orbit Number:


Sor Kaydak, NE Caspian Sea, Kazakhstan

Note: This caption refers to the image versions labeled "NASA's Earth Observatory web site".

This striking image shows saline water of different colors in the Sor Kaydak, a salt marsh that leads into the northeast bulb of the Caspian Sea. The central 50 km of this 180 km-long depression is shown in this astronaut photograph. The Sor Kaydak depression is inundated on occasion by water from the Caspian Sea since it lies at the same elevation—that is, 29 m below global sea level—though separated from the Sea by a low bar of land that is 1–2 m high.

The different colors of marsh water (brown to pink to light green, northeast to southwest) result from the interplay of water depth and resident organisms such as algae. Algae color varies depending on water temperature and salinity. The irregular gray areas at image top left are wet zones between low sand dunes. These interdune flats are whitened with salt derived by evaporation of Caspian Sea water (the sea is just outside the image top left). The jagged line following the colored water (crossing the center of the image top to bottom) is the limit of the wetting zone (or perimeter), an irregular zone influenced by wind and the depth of water in the marsh.

Small cliffs can be seen marking the east margin of the depression that contains Sor Kaydak. Above the cliffs a plateau surface (~200 m above the salt marsh, ~160 m above global sea level) extends eastward for hundreds of km. Here the plateau is occupied by a dense pattern of well heads which appear as a geometric pattern of tan dots. By contrast, the west margin (image left) rises less than 10 m above the marsh altitude. The straight line visible at image center is a pipeline built across the salt marsh which takes oil to a terminal on the Caspian shore 100 km northwest of the area shown here.

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