A new survey of eastern Antarctica has revealed a surprising find: two lakes buried beneath a 4-kilometer-thick ice sheet that rival the famous Lake Vostok in size. The lakes may hold exotic life, and their position along ancient fault lines could shed light on how a nearby mountain range formed.
Earth scientists have so far spied about 145 subglacial lakes in Antarctica. Sandwiched between the ice above and bedrock below, the lakes stay liquid due to a combination of geothermal heat and the crushing pressure of the ice sheet. Lake Vostok, by far the largest of these lakes, is well-mapped, and a Russian team is now drilling through its ice cap in hopes of finding life inside (Science, 28 October 2005, p. 611). But scientists know little about most of the region's lakes, spotted only from sparse radar surveys.
A team led by geologist Robin Bell and glaciologist Michael Studinger, both at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York, revisited two hidden bodies of water glimpsed in earlier surveys. To conduct a more thorough analysis of the lakes, named 90°E and Sovetskaya, the team drew on a suite of data including new satellite images and decades-old gravity measurements, which use differences in the density of ice and water to gauge a lake's depth.
The study found that the lakes are second in size only to Lake Vostok and are nestled in deep depressions. At 2000 square kilometers, 90°E is roughly half the size of Rhode Island and reaches roughly a kilometer deep--about the same as Vostok. Sovetskaya is almost as large, at 1400 square kilometers, and likely as deep. The lakes' depths and the rugged terrain surrounding them suggest that they lie in crevasses along ancient faults, long dormant. Because the depressions that cradle the lakes are so large and deep, the researchers argue the lakes have likely stayed stable through climate changes and have been there since Antarctica was warm and rainy, more than 35 million years ago. If so, this may increase the chances that they harbor life, the team reports in the February issue of Geophysical Research Letters.
The idea that a lot of subglacial lakes form along faults is "very likely to be correct," says glaciologist Garry Clarke of the University of British Columbia in Vancouver, Canada. If this bears out, he adds, "you could use the location of the lakes to map stripes across Antarctica and decide where the tectonic features are." That could help researchers understand mysteries such as the Gamburtsev Mountains, which do not appear to have been shaped by the tectonic activity that helped form other major mountain ranges.