The magnificent ice sheet that blankets Antarctica holds 6.4 million cubic miles (27 million cubic kilometers) of frozen water. From top to bottom, it's over 2.2 miles (3.5 kilometers) thick in some places.
Our global sea level would rise by 190 feet (58 meters) if all that ice melted. As things presently stand, the frigid sheet conceals a hidden world.
More than 379 "subglacial lakes" are caught between Antarctic bedrock and the ice sheet. The lakes retain liquid water, despite the miles (or if you prefer, kilometers) of frozen H2O up above them. Scientists have learned they're often interconnected as well.
Lake Vostok is the biggest of the bunch. Roughly the size of North America's Lake Ontario, the buried landmark has inspired curiosity and controversy for decades.
A Legacy of Exploration
On Jan. 27, 1820, Fabian Gottlieb von Bellingshausen — then a captain in the Russian Imperial Navy — made the first recorded sighting of the Antarctic continent. He'd been leading an expedition whose flagship was called "Vostok," the Russian word for "east."
The USSR later tipped its hat to the man. About 800 miles (1,300 kilometers) from the geographic South Pole, there's a (very remote) research facility the Soviets built in 1957. In honor of Bellingshausen's adventure, it was named Vostok Station.
The name was well-chosen. Researchers divide the Antarctic Ice Sheet into three smaller parts. There's the West Antarctic Ice Sheet, the Antarctic Peninsula Ice Sheet and, last but not least, the East Antarctic Ice Sheet.
Vostok Station sits on the last of these. Because (again) "Vostok" means "east," that makes perfect sense.
While reviewing seismic data that was gathered in the 1950s, Russian geographer Andrey Kapitsa began to suspect there might be a huge liquid lake hiding under the East Antarctic Ice Sheet, somewhere around Vostok Station.
Proof was a long time coming.
Finding Lake Vostok
Scientists can use penetrating radar to measure an ice sheet's thickness. First, high-energy radio waves are sent through glaciers, ice sheets or ice caps. If any echoes bounce back, they might reveal important info about the frozen water's structural makeup.
Back in the 1960s and 1970s, this technology started finding subglacial lakes across Antarctica. It turned out Kapitsa's hunch was right on the money.
A radio-echo survey, and measurements taken via satellite, eventually confirmed there's a giant lake buried near Vostok Station. The journal Nature announced this discovery on June 20, 1996.
More than 2 miles, or nearly 4 kilometers, of ice separate Lake Vostok (as it's come to be known) from the surface. Human hands have never touched it, but seismometers and ice-penetrating radar have given us a decent picture of the lake.
We know it's got an elongated shape. Even though Lake Vostok is around 155 miles (250 kilometers) in length, it's only 31 to 50 miles (50 to 80 kilometers) wide. There's both a northern and a southern basin. Experts say the lake is up to 2,600 feet (800 meters) deep at certain points. And it holds something like 1,300 cubic miles (5,400 cubic kilometers) of liquid water.
All this is quite interesting, but it begs a fundamental question. How can any lake — big or small — persist underneath an expanse of ice taller than any skyscraper without freezing solid?
All Warmed Up
Subglacial lakes need sources of heat. Sometimes, the Earth itself may provide it.
Our planet releases geothermal energy. This heat can radiate upward and melt glacial ice that's made contact with bedrock. Liquid water then accumulates in valleys and other depressed areas on the rocky surface.
Weird as it might sound, some ice sheets provide heat, too. Ice will naturally melt under the right amount of pressure. And a really thick, really heavy ice sheet is going to put lots and lots of pressure on the water molecules at its base.
Lake Vostok's prehistoric origins are a little murky, but for the past 15 to 20 million years (or so), the lake's been covered by ice.
The Search for Life in the Lake
Back in 1999, microbes were found inside ice samples collected just above Lake Vostok. The ice in question may have once been water from the lake's surface which — at some point — froze to the overhanging glacier.
A 2013 study discovered more than 3,000 "unique gene sequences" in subsurface ice associated with Lake Vostok. Nearly half of this genetic material was identifiable; around 94 percent came from bacteria. The authors said they'd also found evidence of more complex organisms, like fungi and small crustaceans.
Critics of the 2013 paper worried that the drilling tools used to gather these ice samples might have been contaminated. If true, the gene sequences collected near Lake Vostok might've actually came from foreign environments. However, lead author Scott Rogers has pushed back against these arguments.
On Feb. 5, 2012, Russian scientists penetrated Lake Vostok for the very first time after drilling through almost 2.5 miles (4 kilometers) of ice. As fate would have it, Andrey Kapitsa had passed away less than one year prior.
Exploring Lake Vostok and other subglacial environments could teach us a thing or two about the possible living conditions on some faraway moons — like Jupiter's Europa or Enceladus of Saturn. Both worlds have liquid oceans underneath shells of ice, making them irresistible targets in humanity's search for extraterrestrial life.