Russia’s Arctic and Antarctic Research Institute (AARI) has been drilling to the lake’s depth of 2.4 miles beneath the surface since 1989, amid fears it could contaminate Lake Vostok with modern bacteria, chemicals and virus strains.

The use of 65 tons of kerosene in the drill to prevent the bore hole from squeezing shut has been the biggest concern.

The petrochemical is known to promote the growth of bacteria.

But the scientists said they used a sensor to warn them of the approach of free water so that they could adjust the pressure inside the hole so none of the kerosene or other drilling liquids would fall into the 6,000-square-mile lake.

The AARI team plans to extract lake water to the surface and let it freeze for later studies as the Antarctic winter’s brutal chill sets in over the next few weeks.

Nearby Vostok Station boasts the world’s all-time recorded lowest temperature of 128.5 degrees Fahrenheit.

AARI researcher Lev Savatyugin said scientists hope to find primeval bacteria in Lake Vostok’s water that could expand the human knowledge of the origins of life.

Lake Vostok is 160 miles long and 30 miles across at its widest point. It is warmed from beneath by geothermal energy.

Top photo: Arctic and Antarctic Research Institute