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IMAGE CAPTION               Antarctic Ice Borehole Probe Project
                            March 16, 2001

Ice and debris layers are seen within the West Antarctic ice 
sheet in this image taken by the downward-looking camera of an 
ice probe designed by NASA's Jet Propulsion Laboratory, Pasadena, 
Calif.    

The image, the first of its kind from deep within an Antarctic 
ice stream, was taken at almost 1,063 meters (nearly 3,488 feet), 
as the probe made its way back up a borehole to the surface.  
Though the process that led to the layering is not yet fully 
understood, scientists think that upstream, ice and gravel have 
frozen onto the base of the ice sheet.  With the ice streams in 
constant motion, water may slide under debris-laden layers, 
lifting them up, allowing the process to repeat. Further research 
on these ice layers could help researchers understand the 
processes going on upstream and learn how ice streams flow and 
stop flowing.  The ball chain, seen in the lower right hand side 
of the image, was used for scale.  The balls are approximately 1 
millimeter in diameter.

The image was obtained during work associated with the Antarctic 
Ice Borehole Probe Project, a collaborative effort of JPL and the 
California Institute of Technology in Pasadena, supported by NASA 
and the National Science Foundation, Arlington, Va.  

The West Antarctic ice sheet, along with the rest of the 
Antarctic ice sheet, holds a potential treasure trove of 
information related to the geological history of this frozen 
continent and the mechanisms by which ice travels from the ice 
sheet to the sea.  Studies show that significant changes in 
glacier melting and flow rates could have a considerable impact 
on global sea levels.
 
The three-month glaciological investigation, from October 2000 to 
January 2001, took place at Stream C, an area in the West 
Antarctic ice sheet where 150 years ago the ice suddenly stopped 
flowing in one area in the middle of the stream.

Photo Credit:  NASA/JPL