A rather surprising geographical feature of Antarctica is that a huge freshwater lake, one of the world's largest and deepest, lies hidden there under four kilometers of ice. Now known as Lake Vostok, this huge body of water is located under the ice block that comprises Antarctica. The lake is able to exist in its unfrozen state beneath this block of ice because its waters are warmed by geothermal heat from the earth's core. The thick glacier above Lake Vostok actually insulates it from the frigid temperatures (the lowest ever recorded on earth) on the surface.

The lake was first discovered in the 1970s while a research team was conducting an aerial survey of the area. Radio waves from the survey equipment penetrated the ice and revealed a body of water of indeterminate size. It was not until much more recently that data collected by satellite made scientists aware of the tremendous size of the lake; the satellite-borne radar detected an extremely flat region where the ice remains level because it is floating on the water of the lake.
The lake was first reached in 2012, when a Russian team finished drilling a hole some 3770 metres down to its surface. They claimed that water samples they obtained from this borehole contained DNA that was unlike known bacteria, suggesting they may have found an unusual native species. But the find is controversial, not least because the samples were contaminated with fluid used to aid drilling. The second attempt reached the lake surface in 2015. The team used the same borehole down to 3400 metres below the surface, after which the holes diverge. This time, the team said they proceeded with extreme caution and were confident that the new samples they retrieved were pristine lake water.

The discovery of such a huge freshwater lake trapped under Antarctica is of interest to the scientific community because of the potential that the lake contains ancient microbes that have survived for thousands upon thousands of years, unaffected by factors such as nuclear fallout and elevated ultraviolet light that have affected organisms in more exposed areas. The downside of the discovery, however, lies in the difficulty of conducting research on the lake in such a harsh climate and in the problems associated with obtaining uncontaminated samples from the lake without actually exposing the lake to contamination. Scientists are looking for possible ways to accomplish this.