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Astronaut Photography of Earth - Display Record
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IdentificationMission: ISS017 Roll: E Frame: 13789 Mission ID on the Film or image: ISS017
Country or Geographic Name: LIBYA
Features: DESERT, DENDRITIC DRAINAGE
Center Point Latitude: 28.3 Center Point Longitude: 16.2 (Negative numbers indicate south for latitude and west for longitude)
Stereo: (Yes indicates there is an adjacent picture of the same area)
ONC Map ID: JNC Map ID:
CameraCamera Tilt: 24
Camera Focal Length: 400mm
Camera: N2: Nikon D2Xs
Film: 4288E : 4288 x 2848 pixel CMOS sensor, RGBG imager color filter.
Percentage of Cloud Cover: 10 (0-10)
NadirGMT Date: 20080819 (YYYYMMDD) GMT Time: 143609 (HHMMSS)
Nadir Point Latitude: 29.5, Longitude: 17.0 (Negative numbers indicate south for latitude and west for longitude)
Nadir to Photo Center Direction: Southwest
Sun Azimuth: 264 (Clockwise angle in degrees from north to the sun measured at the nadir point)
Spacecraft Altitude: 191 nautical miles (354 km)
Sun Elevation Angle: 36 (Angle in degrees between the horizon and the sun, measured at the nadir point)
Orbit Number: 3851
CaptionsDesert Erosion, A Modern Libyan Landscape
This detailed astronaut photograph shows the classic patterns of an eroded desert landscape, about 300 kilometers (190 miles) south of Libya’s Mediterranean coast. Widespread indented patterns are low escarpments and stream terraces generated by stream erosion—on those few occasions in any decade when enough rain falls for streams to flow. The only areas where sediment is being deposited are the streambeds, which appear in this image as sinuous zones with a distinct component of black minerals. These minerals give the streambeds a darker color than adjacent low escarpments (image top left and lower left). The sediment comes from a volcanic landscape immediately upstream to the west.
Other stream-generated features are several relict stream banks (indicated by ovals); one area even preserves both (parallel) banks of the original stream (far right oval). The ancient stream banks were cemented by minerals such as calcium carbonate and gypsum, introduced by the streams when they were active, probably during wetter climates in the past 2 million years. Relict stream courses show prior positions of streams, and help tell the region’s paleoclimate story. They also provide Earth analogs for similar features on Mars.
The lack of vegetation is the first indication of the great aridity of the region, but sand dunes also appear as sinuous lines oriented perpendicular to the dominant northeasterly wind direction (transverse dunes). If the dominant wind direction remains the same, these transverse dunes would be expected to move further to the southwest over time (towards the top left). Some of the dunes cross the river courses, showing how seldom the rivers flow.
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Recommended Citation: Earth Science and Remote Sensing Unit, NASA-Johnson Space Center. "The Gateway to Astronaut Photography of Earth." .