Analysis of an Antarctic ice core suggests that bacteria may live in a fresh-water subglacial lakeÐan extreme environment that may be Earth's closest analog to a frozen moon of Jupiter. Evidence for the microbial life thousands of meters below the ice sheet is presented in a paper by a team headed by University of Hawai'i Oceanographer David Karl. The paper is one of two on the subject appearing in the Dec. 10 edition of Science magazine.
"The subglacial lakes of East Antarctica may be among the most isolated ecosystems on Earth and could serve as terrestrial analogues to guide the design of samplers and experiments for life probe missions to the ice-covered ocean of the Jovian moon Europa," concludes Karl.
Karl and his group are part of an international team of scientists examining the ice below Vostok Station, a Russian scientific outpost in the Antarctic interior. Lake Vostok is one of nearly 80 subglacial lakes discovered and mapped using airborne radio-echo soundings and other techniques. Roughly the size of Lake Ontario, Lake Vostok is the largest and deepest of the lakes, whose fresh water is kept liquid by the pressure of the overlying ice and, perhaps, by geothermal heating.
U.S., French and Russian scientists have studied fragments taken from an ice core drilled 3,600 meters (about 11,700 feet) into the ice covering the lake. Drilling has been halted roughly 120 meters (393 feet) above where the ice and liquid water meet, to prevent possible introduction of material that would contaminate the water, while scientists debate how to proceed.
"This lake and others like it, may contain previously undescribed relic populations of microorganisms that are adapted for life in these presumably oligotrophic (low-nutrient, low-biomass and low-energy flux) habitats," says Karl.
Karl and colleague John C. Priscu, of Montana State University, have found bacteria within the "accreted" ice, which is believed to have refrozen from the liquid waters of the lake, suggesting that the lake can support life in an extremely cold environment, cut off from a ready supply of nutrients and light. Although Priscus's work indicates the bacteria are biologically similar to other organisms known to science, scientists "don't know how 'lake-like' this accreted water is" and whether it may contain larger, more diverse populations, according to Karl.
It may, however, indirectly provide evidence that microbes could thrive in other similarly hostile places in the solar system.
In addition, the Antarctic ice cores provide a continuous climate record stretching back more than 400,000 years. Obtaining sediment samples from the bottom of Lake Vostok could extend the climate record to cover millions of years.
Both Karl and Priscu receive research funding from the National Science Foundation. Karl's group includes D. F. Bird, of the Université du Quebec á Montreal, and K. Björkman, T. Houlihan, R. Shackelford and L. Tupas of the University of Hawai'i at Manoa.
Journal
Science