In Pictures: Antarctica's "Ghost Mountains"

In 2008 and 2009 the international team crisscrossed the Gamburtsev area—roughly the size of New York State—with a radar-equipped airplane, which allowed them to peer through the ice to "see" the underlying terrain. The radar also revealed water pockets beneath the ice, Bell said. That's important, because understanding the subglacial plumbing helps scientists determine what will happen to the Antarctic ice sheet as global warming intensifies. (See "Antarctica Ice Loss Faster Than Ten Years Ago.")

A researcher prepares a plane for radar duty during a 2008 expedition over Antarctica's ice-buried Gamburtsev Mountains. On the surface the ice is often runway flat, revealing nothing of the underlying terrain, which can be as deep as 15,700 feet (4,800 meters). Peering beneath the ice requires modifying the plane with radar antennas mounted to the wings, a bone-chilling job in even the best Antarctic conditions.

At the surface, Antarctica can be a fairyland of complex features, such as this ice cave photographed during a Gamburtsev Mountains expedition in 2008. But the landscape beneath the ice has long been a mystery, requiring painstaking work to unmask. "We flew a lot," expedition leader Robin Bell told National Geographic News by email. "Twelve months ago, the map was fuzzy," she said. But with multiple flights across a grid 430 miles (700 kilometers) long and 155 miles (250 kilometers) wide, the details began appearing. "Slowly the map filled in," she said, "and we saw the mountain range unfold."

Strong winds on a day in 2009 confined expedition members to camp—and delayed the radar flights that eventually brought to light the hidden peaks, valleys, and streams of the Gamburtsev Mountains. In some places under the Antarctic ice, expedition leader Bell said, it appears that liquid water flows down some of Gamburtsev's ancient valleys. "But there are other places where the [moving] ice sheet is simply going to pull the water and drag it right over the ridges and down the other side," she said, "right over the highest peaks."

Like the tips of icebergs breaking the surface of a pale sea, mountains near the South Pole show that many Antarctic summits—unlike the Gamburtsevs, which lie farther east—remain unconquered by ice. Any kind of scientific study presents unique challenges in Antarctica. "We needed to get people, equipment, and fuel into the middle of the ice sheet," expedition leader Bell said. Among the complications: fuel turned to unburnable jelly in the cold and the high altitude made oxygen bottles necessary for breathing. By the time the team was ready to go home, she said, they were exhausted.

In one of the most detailed images yet of Antarctica's ice-hidden Gamburtsev Mountains, a picture based on 2008 and 2009 radar readings shows the peaks in their unexpectedly spiky splendor, though the image's vertical scale has been exaggerated. Studying the mountains' topography can help determine when and how the Gamburtsevs were formed—a longstanding mystery. The existence of river valleys indicates that the mountains predate present-day ice-covered Antarctica, but no one is sure by how much. The Gamburtsevs are likely younger than 500 million years old, Bell said. If they were older than that, they'd show signs of deformation from a prehistoric collision between Australia and Antarctica. Not to mention that, if the Gamburtsevs had been around for 500 million years, they'd have long ago eroded into nothing, she added.

In what expedition member Michael Studiger called a "million-dollar view," Antarctica's active Mount Erebus volcano peeks out from behind a hill near the Ross Ice Shelf (interactive Antarctica map) in 2008—far from the Gamburtsev Mountains. Team members headed for the remote field camp had to participate in a mandatory two-day survival course near the volcano loosely referred to as Snow School or Happy Camper School. Expedition leader Robin Bell thinks the Gamburtsevs are far older than Mount Erebus. They may have been formed about 250 million years ago, when Antarctica had already eased into its current position above the South Pole. It was a warmer time, Bell said, when erosion could have produced the valleys seen in the new ice-penetrating radar images. Then the ice came and buried the valleys, not to mention the peaks—leaving them, until recently, Earth's last unexplored mountain range.