From: Jet Propulsion Laboratory
Posted: Friday, March 16, 2001
Scientists have had their first inside look at ice layers, frozen debris and a surprising channel of water deep beneath an Antarctic ice stream, thanks to an ice probe designed by NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Plunged more than 1,200 meters (more than 3,900 feet) down four boreholes drilled in the West Antarctic ice sheet, JPL's probe paves the way for the development of technology capable of withstanding extreme environments on Earth and other planets.
The Antarctic Ice Borehole Probe Project, a collaborative effort of scientists at JPL and the California Institute of Technology in Pasadena, looked into the dynamics of the West Antarctic ice sheet. The Antarctic ice sheet, equal in size to the United States and Mexico combined, holds a potential treasure trove of information related to the geological history of this frozen continent and the mechanisms by which ice flows from this area to the oceans. Studies show that significant changes in glacier melting and flow rates could have a considerable impact on global sea levels.
"This project fits into the bigger picture of planetary studies," said Dr. Frank Carsey, JPL's principal investigator on the project. "It provides us with some understanding of how to observe what goes on deep in ice caps -- Earth's ice caps, Martian ice caps and ice caps on Europa." Europa is an ice-covered moon of Jupiter.
The glaciological investigation took place at Ice Stream C, an area in the West Antarctic ice sheet where 150 years ago the ice suddenly stopped flowing in one area in the lower part of the stream. This so-called "sticky spot," currently flowing at a rate of 2 meters per year (about 6 feet), greatly differs from its neighboring streams, flowing at approximately 400 meters (1,300 feet) per year.
Equipped with two cameras and lights, JPL's ice probe revealed what appears to be a basal water system, or series of water channels at the base of the ice stream. In places, this water-filled cavity measured approximately 1.4 meters deep (4.6 feet). Based on previous calculations, researchers expected the depth of a water basal cavity to be only in the millimeter range.
To the researchers' surprise, they also found rock and other debris embedded in the ice much higher than expected. It was believed that frozen debris would be found no higher than two meters (almost seven feet) off the base of the ice stream. In contrast, the visual data shows frozen debris some 26 meters (85 feet) off the base, which has yet to be explained.
A layering effect in the ice was also uncovered by the probe. Though not yet fully understood, it is thought that, upstream, ice and gravel have frozen onto the base of the ice sheet. With the ice streams constantly moving, water may slide under debris-laden layers, lifting them up, allowing the process to repeat.
"The layered information will turn out to be very interesting," said Carsey. "These layers tell us about processes upstream." By analyzing these ice layers, researchers may learn how ice streams flow and stop flowing.
The team's findings open up the doors to further glaciological research. "With the probe, we have now left the dark ages," said Hermann Engelhardt, Caltech's principal investigator on the project.
JPL hopes to advance the probe's technology in the next year or two, adding biological sensors to search for evidence of life in the Antarctic ice sheet and eventually on other planets. Microbes are known to reside under mountain glaciers, where it is warmer and there are nutrients from impurities found between water crystals.
"These locations are very old places. Some, such as on Mars, are hundreds of millions of years old," said Carsey. The base of a planet's polar cap chronicles the planet's climate and can reveal much about its history and biology, he said.
Images of the team's findings are available at http://www.jpl.nasa.gov/pictures/iceprobe .
The Antarctic Ice Borehole Probe Project is a collaborative effort of JPL and Caltech, supported by NASA, Washington D.C., and the National Science Foundation, Arlington, Va. The ice probe was developed by JPL, a division of Caltech.
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