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Planetary News: Earth (2007)Earth from Space: Iceberg in the South Atlantic OceanJune 20, 2007
This astronaut photograph taken from the International Space Station (ISS) is a close-up of the remains of a giant iceberg -- designated A22A -- that broke off Antarctica in 2002. The iceberg was photographed on May 30 at 49.9 degrees south latitude, 23.8 degrees west longitude, which is about a third of the distance from South America towards Cape Town, South Africa. A22A is one of the largest icebergs to drift as far north as 50 degrees south latitude, bringing it beneath the daylight path of the ISS. Crew members aboard the ISS were able to locate the ice mass and photograph it, despite the great masses of clouds that often accompany winter storms in the Southern Ocean. The crew’s viewing angle was oblique (not looking straight down) from a point to the west of the berg, and the time of day was early afternoon. Dimensions of A22A in early June were 49.9 by 23.4 kilometers (31.0 by 14.5 miles), making it seven times the area of Manhattan Island. Once the ISS crew had located the iceberg, they managed to photograph it successfully with the "long", 800-millimeter lens that provides close-up photos. Handling the longer lens requires practice. Because of the speed of the spacecraft and the length of the lens, it is necessary for the astronaut to "track" the target, that is, to swing the camera slowly to keep the target in the middle of the camera's view finder. If the photographer tracks too slowly or too quickly, the image looks smeared. The long lens only shows a small part of the iceberg. A series of parallel lines can be seen in the lower image. These are probably "hummocks," dunes of snow that have solidified, and they date back to the time when the iceberg was connected to Antarctica. The image also shows a developing fracture in the ice. Images of the iceberg are being acquired from the ISS to support a study of massive icebergs -- part of NASA International Polar Year activities. The study will increase understanding of the way ice sheets evolve as climate changes. When large masses of ice float into warmer waters north of their usual latitudes, they undergo change at rapidly increased rates. Changes that would take decades to occur in Antarctica can happen in a few years or even months in the warmer conditions at 50 degrees south latitude. The crew of the ISS will continue to collect imagery of the accelerating breakup of iceberg A22A as weather, orbital, and illumination conditions allow. More information, including Webcams, on the studies conducted on A22A and at other places in the Antarctic can be found at www.thistle.org and the National Snow and Ice Data Center’s Icetrek Website. |
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