Page 2/2 - Posted March 4, 2015
Navigating IceMole through ice no easy task
Previous tests on different glaciers in Europe, as well on Canada Glacier in Taylor Valley last year, found that each glacier is unique, according to German engineer Gero Francke. That means the behavior of the drill for each deployment is different.
“The difficulties include the navigation,” Francke added. “Down there you are blind. You have to have the systems that tell you your position and orientation in the ice.”
One of the key pieces of technology used to navigate involves sending acoustic pulses from the surface into the ice. Each “ping” can be measured based on its propagation time between the top of the glacier and the IceMole to trilaterate its position.
“It’s similar to a GPS but using different kinds of waves,” Heinen said. “We are using sound to track the position of the IceMole. Navigation in ice is not common.”
Complementary attitude-determination technology integrated into the IceMole is given by an inertial measurement unit and a magnetometer. A sophisticated post-processing sensor fusion serves as decision support for the operator as well.
Other members of the MIDGE team employed different technologies to pinpoint where in the glacier to send the probe.
The brine reservoir itself – possibly the remnant of an ancient sea that receded millions of years ago only to be trapped under the ice – is believed to be several kilometers farther away from Blood Falls up the glacier. Its depth and location would make sampling directly from the source an even greater technological challenge.
Instead, the team focused on locating the channel through which the brine percolates from the reservoir to the surface at Blood Falls.
“We have really good evidence that there is a passageway for water to flow through this very cold ice,” noted Slawek Tulaczyk, a professor in the Earth and Planetary department at the University of California Santa Cruz.
Some of the evidence came from strings of thermometers deployed into boreholes based on radar surveys on the glacier in 2013-14. The thermometers are capable of detecting heat fluxes in the ice. The brine, which remains in liquid form despite being minus 6 degrees Celsius, partly freezes as it rises to the surface through the minus 15-degree ice. That releases a tremendous amount of heat.
Recent heat flux measurements from the thermometers indicated a relatively new injection of water into the subglacial system shortly before the IceMole was deployed, according to Tulaczyk.
Other team members used seismometers to image the ice and bedrock below, as well as high-precision GPS units to track glacial movement, such as cracks in the ice that might be caused as the water pushes through the glacier. A new technique used this year involved electromagnetic resistivity, which employs electromagnetic waves to find conductive material within the ice, such as the hypersaline brine.
“In a sense, we’re not just trying to get a three-dimensional view of the glacier, but a four-dimensional view,” said Jake Walter, a research scientist at the Institute for Geophysics at University of Texas who is involved in the seismic survey of the glacier. “We’re trying to see how this system evolves over time.”
Mikucki’s own interest in Blood Falls has certainly evolved over time since she was a Masters student at Portland State University and first saw a picture of Antarctica’s most outlandish-looking feature.
“It offers us a portal, or window, to the subglacial world … a sample of material from that ice-covered interior,” she said. “It tells us what might be living below the ice of the continent. There are no large animals or trees on Antarctica anymore. It’s a microbial continent.”
NSF-funded research in this article: Jill Mikucki, University of Tennessee in Knoxville, Award No. 1144178 ; Slawek Tulaczyk, University of California-Santa Cruz, Award No. 1144192 ; Erin Pettit and Charles Meertens, University of Alaska Fairbanks, Award No. 1144177 ; Berry Lyons, The Ohio State University, Award No. 1144176 . The Enceladus Explorer collaboration is funded by the DLR Space Administration and comprises the following German universities: FH Aachen University of Applied Sciences, RWTH Aachen University, Braunschweig University of Technology, University of Bremen, Universität der Bundeswehr Munich, and University of Wuppertal.