Antarctica
McMurdo Dry Valleys
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Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team

4 December 2009
Dry Valleys, Antarctica

The McMurdo Dry Valleys are a row of valleys west of McMurdo Sound, Antarctica, so named because of their extremely low humidity and lack of snow and ice cover. Photosynthetic bacteria have been found living in the relatively moist interior of rocks. Scientists consider the Dry Valleys to be the closest of any terrestrial environment to Mars.

With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of about 50 to 300 feet, ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched Dec. 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The broad spectral coverage and high spectral resolution of ASTER provides scientists with critical information for surface mapping and monitoring of dynamic conditions and temporal change.

SOURCE: NASA

McMurdo Dry Valleys
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Map of the McMurdo Sound and the Dry Valleys.

The McMurdo Dry Valleys are a row of valleys in Antarctica located within Victoria Land west of McMurdo Sound.[1] The region is one of the world's most extreme deserts, and includes many interesting features including Lake Vida and the Onyx River, Antarctica's longest river.

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McMurdo Dry Valleys, Antarctica
This image was acquired by Landsat 7s Enhanced Thematic Mapper plus (ETM+) instrument on December 18, 1999.

Credit: Image by Robert Simmon, based on data provided by the NASA GSFC Oceans and Ice Branch and the Landsat 7 Science Team

One of the few areas of Antarctica not covered by thousands of meters of ice, the McMurdo Dry Valleys stand out in this satellite image. For a few weeks each summer temperatures are warm enough to melt glacial ice, creating streams that feed freshwater lakes that lie at the bottom of the valleys. Beneath a cap of ice these lakes remains unfrozen year-round, supporting colonies of bacteria and phytoplankton. Over the past 14 years, however, summers have been colder than usual, and the lakes are becoming more and more frozen. If the trend continues, the biological communities they support may go into hibernation.

Most of Antarctica has cooled along with the Dry Valleys, in contrast to much of the rest of the Earth, which has warmed over the past 100 years. No one knows if the trend is related to global climate, or just a quirk in the weather.

Climate

 
The Dry Valleys are so named because of their extremely low humidity and their lack of snow or ice cover. They are also dry because, in this location, the mountains are sufficiently high so that they block seaward flowing ice from the East Antarctic ice sheet from reaching the Ross Sea. At 4800 square kilometers, the valleys constitute around 0.03% of the continent, and form the largest ice-free region in Antarctica. The valley floors are covered with loose gravel, in which ice wedge polygonal patterned ground may be observed.[2]

The unique conditions in the Dry Valleys are caused, in part, by katabatic winds: these occur when cold, dense air is pulled downhill by the force of gravity. The winds can reach speeds of 320 km/h (200 mph), evaporating all water, ice and snow.[3]

Geology

 
The valleys cut through the Beacon sandstone, as well as older granites and gneisses of the Ross Orogeny. Tills, deposited directly from ice, dot this bedrock landscape. These tills are relatively thin and patchy, and differ markedly from the extensive, mud-rich tills of the Laurentide ice sheet in the Northern Hemisphere. One reason for the difference is that most of the tills in the Dry Valleys were deposited from cold-based ice (ice with basal temperatures below zero C), whereas the Laurentide ice sheet was largely wet-based, with significant melting at the base and at the glacier surface.

Biota

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Blood Falls seeps from the end of the Taylor Glacier into Lake Bonney. The tent at left provides a sense of scale for just how big the phenomenon is. The phenomenon is due to leaks from a reservoir of ancient saltwater buried under the glacier. Ferrous ions dissolved in the water oxidize on contact with the atmosphere, and precipitate as insoluble reddish ferric salts. 26 November 2006 SOURCE

Unusual bacteria have been found in Blood Falls at the tongue of the Taylor Glacier, above the ice-covered surface of Lake Bonney in Taylor Valley.

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Mummified Seal Carcases in McMurdo Dry Valleys, Antarctica.
The image is a scan of my old print. The image was taken by Mila Zinkova
 
Mummified seal carcass


Endolithicphotosynthetic bacteria have been found living in the Dry Valleys, sheltered from the dry air in the relatively moist interior of rocks. Summer meltwater from the glaciers provides the primary source of soil nutrients. Scientists consider the Dry Valleys perhaps the closest of any terrestrial environment to the planet Mars, and thus an important source of insights into possible extraterrestrial life. Anaerobic bacteria whose metabolism is based on iron and sulfur live in sub-freezing temperatures under the Taylor Glacier, staining red the ice emerging at Blood Falls.[4][5]

Part of the Valleys was designated an environmentally protected area in 2004.

Major geographic features

Valleys

Lakes

Some of the lakes of the Dry Valleys rank among the world's most saline lakes, with a higher salinity than Lake Assal (Djibouti) or the Dead Sea. The most saline of all is small Don Juan Pond.

Rivers
References
  1. Rejcek, Peter (November 29, 2007). "In the cold of the night" (web). Science team to extend seasonal work until April to study lake ecosystem in the McMurdo Dry Valleys. The Antarctic Sun
  2. Bockheim, J. G. (2002). "Landform and Soil Development in the McMurdo Dry Valleys, Antarctica: A Regional Synthesis" (web). Arctic, Antarctic, and Alpine Research (Arctic, Antarctic, and Alpine Research, Vol. 34, No. 3) 34 (3): 30817. doi:10.2307/1552489
  3. Lloyd, J & Mitchinson, J: "The Book of General Ignorance". Faber & Faber, 2006.
  4. John Timmer. Ancient, frozen ecosystem produces blood-red ice flows, Ars Technica, 16 April 2009. Accessed 17 April 2009.
  5. Mikucki, Jill A.; Ann Pearson, David T. Johnston, Alexandra V. Turchyn, James Farquhar, Daniel P. Schrag, Ariel D. Anbar, John C. Priscu, and Peter A. Lee (17 April 2009). "A Contemporary Microbially Maintained Subglacial Ferrous "Ocean"". Science 324 (5925): 397400. doi:10.1126/science.1167350. PMID19372431
  6. http://www.antarcticanz.govt.nz/downloads/environment/Map.pdf - [No longer available]
Related Links:
The Dry Valleys of Antarctica
"Sure, the lion is king of the jungle, but airdrop him into Antarctica, and he's just a penguin's bitch."    Dennis Miller.
On this page:
1997

Images by Billy, Laura Connor and Effie Jarret

The dry valleys are strange: except for a few steep rocks they are the only continental part of Antarctica devoid of ice. Located in the Trans-Antarctic Range, they correspond to a mountain area where evaporation (or rather, sublimation) is more important than snowfall, thus all the ice disappears, leaving dry barren land.

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[DryValleyFrontGlacier.jpg]Disappearing glacier in the Dry Valleys, Antarctica
Disappearing glacier in the Dry Valleys, Antarctica

Here a glacier coming from the continental ice field flows down the valley and just dries out. In summer there can be rivers in the Dry Valleys. Moss and some other form of vegetation grow. Some lakes have strange characteristics, like lake Vanda, always covered with ice, but with salt-saturated liquid water underneath and very mysterious biology. Mummified bodies of seals have been found in those parts, hundreds of kilometers from the sea.

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[DryValleyIceFall.jpg]Sublimating ice in the Dry Valleys, Antarctica.
Sublimating ice in the Dry Valleys, Antarctica

The Dry Valleys are a favorite exploration spot for geologists and microbiologists. I've never been there, those pictures were taken by Laura Connor and Effie Jarret who flew over them several times during their remote sensing missions.




1977

Images by Thierry Cappelle
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[Cappelle100.jpg]Return flight from Dome C to McMurdo above the Dry valleys.
Return flight from Dome C to McMurdo above the Dry valleys
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[Cappelle101.jpg]In the Dry Valleys: glacial tongue coming down from the inlandsis towards the bottom of the valley. Height of the ice: 30 to 50 meters.
In the Dry Valleys: glacial tongue coming down from the inlandsis towards the bottom of the valley.
Height of the ice: 30 to 50 meters.
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[Cappelle102.jpg]Another glacial tongue coming down from the inlandsis towards the bottom of the valley. About 50 meters high.
Another glacial tongue coming down from the inlands is towards the bottom of the valley. About 50 meters high

If you want more info on the Dry Valleys, there's an excellent site.

SOURCE: The Dry Valleys of Antarctica

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