Status Report

Photo: Rio Negro floodplain in Patagonia, Argentina As Seen From Orbit

By SpaceRef Editor
February 14, 2011
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The Rio Negro floodplain in Patagonia, Argentina is featured in this image photographed by an Expedition 22 crew member on the International Space Station. The Rio Negro is recognizable by astronaut crews from orbit as one of the most meandering rivers in South America. This is well illustrated in this view, where the entire river floodplain (approximately 10 kilometers wide) is covered with curved relics of channels known as meander scars. The main channel of the river, flowing south at this point–60 kilometers south of the city of Choele Choel (not shown)–appears in partial sun glint at right. Sun glint occurs when light is reflected off a water surface directly back towards the viewer, imparting a silvery sheen to those areas.

When meander scars contain water they are known as oxbow lakes, some of which are also highlighted by sun glint in the image. Meander scars show the numerous past positions of river bends, produced as the river snaked across the plain in the very recent geological past. The Rio Negro is a dramatic example of how mobile a river can be. The orange tint to the water in one of the oxbow lakes (center) could result from orange salt-loving algae. Their appearance here would be unusual since floodplain lakes are usually too fresh for algae blooms. But an explanation may lie in the location of the Rio Negro on the margin of Argentina’s arid Patagonian region with annual rainfall less than 12 inches (300 mm). Evaporation in this cloudless region could be high enough for some lakes to become salty.

The Rio Negro flows generally southeast from the Andes Mts. to the Atlantic Ocean. Its floodplain supports the biggest pear- and apple-growing region of Argentina. Rectangular farm boundaries can be seen at bottom center. The river also hosts the world’s longest kayak regatta (653 kilometers), which lasts six days. ISS022-E-019513 (4 Jan. 2010) — high res (1.1 M) low res (82 K)

SpaceRef staff editor.