For 15 million years, an icebound lake has remained sealed deep beneath Antarctica’s frozen crust, possibly hiding prehistoric or unknown life. Now Russian scientists are on the brink of piercing through to its secrets.

“There’s only a bit left to go,” Alexei Turkeyev, chief of the Russian polar Vostok Station, told Reuters by satellite phone. His team has drilled for weeks in a race to reach the lake, 3,750 meters (12,000 ft) beneath the polar ice cap, before the end of the brief Antarctic summer.

It was here that the coldest temperature ever found on Earth — minus 89.2 Celsius (minus 128.6 Fahrenheit) — was recorded.

With the rapid onset of winter, scientists will be forced to leave on the last flight out for this season, on Feb 6.