|Date:||2/28/01 2:07:22 PM Pacific Standard Time|
To: email@example.com (Kent Steadman)
Soaring below Vostok
From Feb 11, 2001 issue of the Antarctic Sun ( Last issue of the year)
At first glance Lake Vostok is just flat and white, but Tom Richter had three weeks to look at it more closely.
He spent four hours a day flying back and forth over the frozen lake. The best views weren't out the window of the Twin Otter plane, but in data from instruments that "see" through the ice sheet, measuring the depth and altitude of the ice, gravitational attraction, and magnetism of the earth.
"You could just look and see there was something interesting going on," Richter said. "There's rough, regular, rocky ground and then all of a sudden you could see some flat lake surface."
The American camp at Lake Vostok, above, surrounded by flat, white terrain. Photos provided by SOAR.
Richter was at Vostok with the rest of the SOAR team, the Support Office for Aerogeophysical Research, to gather data for scientists trying to better understand the hidden lake, which is the size of Lake Ontario.
"Why the lake's there nobody knows and that's why we're there," Richter said. "I don't know if we're going to be able to find out either."
Researcher Michael Studinger thinks he will find an answer in the 30 gigabytes of data SOAR collected in 36 flights.
"It's the first detailed image of the lake itself," Studinger said. "We are most interested in getting the geologic setting of the lake and also the depth of the lake."
Every second the equipment recorded the gravitational attraction, six radar readings and 10 measures on the magnetometer. The altimeter gave the altitude of the ice to within 10 to 20 centimeters. Radar showed the terrain below the flat ice changed from rolling plains on one side of the lake to mountains on the other. The lake itself appeared to be in a basin, below two miles (three to four km.) of ice.
The SOAR team loads equipment into a Twin Otter plane. The equipment is used to measure changes in magnetism, gravity, altitude and ice depth, which will help scientists map and understand Lake Vostok. Photo provided by SOAR.
The findings will help scientists decide between two theories for the creation of the lake. One scenario is that the lake was created by erosion. The second possibility, and the one Studinger said preliminary data supports, is that changes in the earth's crust formed the lake.
The evidence is a huge magnetic anomaly on the east coast of the lake's shoreline. As the first SOAR flight crossed over to the lake's east side, the magnetometer dial swung suddenly. The readings changed almost 1,000 nanotesla from the normal 60,000 nanoteslas around Vostok. A tesla is the standard measure of magnetism. Studinger typically finds anomalies of 500-to-600 nanotesla in places where volcanic material has poured out of the ground
"When we first saw this huge magnetic anomaly, that was very exciting," Studinger said.
Usually magnetic anomalies are much smaller and it takes some effort to distinguish the anomaly from normal daily changes in the magnetic field. In this case there was no confusion.
"This anomaly is so big that it can't be caused by a daily change in the magnetic field," Studinger said.
The anomaly was big in another way, encompassing the entire Southeast corner of the lake, about (65 b 46 miles) 105 km by 75 km. The size and extremity of the magnetic anomaly indicated the geological structure changes beneath the lake, and Studinger guessed it might be a region where the earth's crust is thinner.
To create the type of topography found at Lake Vostok, the earth's crust was probably stretched, thinning one to three percent as it pulled taut, Studinger said.
While the SOAR team flew, charting the lake from above, Studinger set up seismic stations to study the lake through the ground. He'll learn more about the crustal structure under the lake from the way seismic waves travel from earthquakes around the world travel through the lake. In 22 days the sensors recorded eight earthquakes, including a 6.9 magnitude quake near Kodiak, Alaska.
Researchers are also interested in the interaction between the ice sheet and the water beneath. The ice sheet moves over the lake at about four meters a year. As it moves, it scrapes the ground and carries particles into the lake.
"That's a way to get nutrients into the lake, which would be important for the ecosystem," Studinger said.
Insulated beneath the ice, the water is warmed by the earth itself. The warm water at the bottom of the lake then rises and melts the bottom of the ice sheet in places, so small currents circulate through the lake.
"What we observe is there are regions where there's melting going on and regions where there's refreezing," Studinger said.
But all these observations are done through the ice. Nobody has actually sampled the lake water itself yet, though Russian scientists have drilled to within a few hundred feet.
SOAR was really just scouting out the area for that next step, touching the water itself. Studinger and his colleagues at Lamont-Doherty Earth Observatory of Columbia University will spend the next two years analyzing the data SOAR collected and writing up the results. Once fully analyzed, the data will show where the sediments are in the lake bottom, how thick they are and where there are upwellings of water.
"One of the important things with this data is it will help to make a decision on a drilling location," Studinger said.
Will continue looking around for info;
Also found an interesting Japanese site
Strangely called Vostok: Home Page of Motokawa Lab English