Biologists have extracted mineral-eating microbes from a lake buried a half mile below the surface of the West Antarctic Ice Sheet, according to a new study published in Nature.
Earlier claims of similar microbes drawn from a different Antarctic lake, say the study's authors, were controversial because the samples had been contaminated—a problem eliminated in this case by especially careful drilling techniques.
"The report is a landmark for the polar sciences," writes Martyn Tranter, a geochemist at the University of Bristol, England, who was not involved in the study, in a commentary also published in Nature.
It's also a landmark in the science of astrobiology, the search for life on other worlds. In recent years, scientists have come to understand that life can thrive in a much wider range of environments than they once believed, including superheated water at the bottom of the ocean and ice caves in Greenland. That suggests that extraterrestrial life might also exist in places once thought uninhabitable.
This new identification of microbes in subglacial Lake Whillans, a 6-foot-deep, 20-square-mile (1.8 meters, 52 square kilometers) body of water kept liquid by heat from the bedrock below and friction from glaciers moving over that bedrock, just adds to the possibilities. The authors' findings, Tranter writes, "beg the question of whether microbes could eat rock beneath ice sheets on extraterrestrial bodies such as Mars."
Antarctica Extremophiles
The Lake Whillans microbes, which come from nearly 4,000 distinct species or "operational taxonomic units" (groups of species with similar characteristics), are chemoautotrophs, meaning they get their energy not from sunlight nor from other organisms that live on sunlight, but rather from minerals dissolved in the water, including nitrites, iron, and sulfur compounds.
Given their ability to exist without light or access to organic food sources, the microbes could also be a model for life on Jupiter's ice-covered moon Europa or Saturn's Enceladus.
To prevent contamination of their samples, the scientists used hot water to drill down through the ice—and although the heat alone would have killed any bacteria that tried to hitch a ride down, the team took additional precautions.
"What we've seen so far is very novel," Christner said. "But that novelty comes largely from our own ignorance." The more places biologists look for at least some type of life, it seems, the more previously unsuspected species they seem to find.
