The scale of the AGAP project required international co-operation
Scientists have completed their mission to map one of the most extraordinary mountain ranges on Earth.
The Gamburtsevs are a set of peaks equal in size to the European Alps, but they are hidden deep under the ice in the middle of the Antarctic continent.
The survey data gathered by the multi-national team working in harsh, sub-zero temperatures will help resolve the mystery of why the range exists at all.
Their presence, when first discovered in the 1950s, was totally unexpected.
Scientists thought the interior of the continent would be relatively flat.
Modern-day remote-sensing technology reveals quite the opposite - a very jagged landscape, albeit buried under up to 4km of ice.
The data will be analysed by researchers in the coming months
"We can confirm they are there; we've seen them under the ice," said Dr Fausto Ferraccioli from the British Antarctic Survey.
"Not only are they similar in dimension to the European Alps, but they are also similar in aspect: we see very sharp peaks and valleys which are remarkably similar to the Alps themselves," he told BBC News.
"It all adds to the mystery - from the tectonic perspective of how these mountains were created; and from the glacial history perspective of how the East Antarctic ice sheet was formed and didn't erode these peaks."
The AGAP (Antarctica's Gamburtsev Province) project comprised scientists, engineers, pilots and support staff from the UK, the US, Germany, Australia, China and Japan.
They established two field camps deep in the Antarctic interior.
Aircraft swept back and forth across the ice, mapping the shape of the sub-glacial mountains using ice-penetrating radar.
Other instruments measured the local gravitational and magnetic fields.
Some 120,000km were flown, the equivalent of three trips around the globe. In total, over 20% (one-fifth) of the East Antarctic Ice Sheet was explored.
EXPLORING THE SUBGLACIAL GAMBURTSEV MOUNTAINS
1. Aircraft used radar to detect ice thickness and layering, and mapped the shape of the deeply buried bedrock
2. The planes also conducted gravity and magnetic surveys to glean more information about the mountains' structure
3. By listening to seismic waves passing through the range, scientists could probe rock properties deep in the Earth
Information on the deeper structure of the Gamburtsevs was gleaned from a network of seismometers that listened to earthquake signals passing through the rock from the other side of the globe.
"The temperatures at our camps hovered around -30C, but three kilometres beneath us at the bottom of the ice sheet we saw liquid water in the valleys," explained AGAP US co-leader Dr Robin Bell, of the Lamont-Doherty Earth Observatory at Columbia University, New York, US.
"The radar mounted on the wings of the aircraft transmitted energy through the thick ice and let us know that it was much warmer at the base of the ice sheet."
The range covers a region at least 700km by 250km. The highest peak is about 2,800m above sea level. The deepest valley is around 800m below sea level.
Researchers believe the Gamburtsevs would have been the starting point for the great glaciers that eventually spread out to cover the entire polar region when it was plunged into a deep freeze more than 30 million years ago.
In their data, scientists hope to pinpoint the best place to drill a core from the ice. Ancient air trapped in the in snow layers as they were laid down could provide remarkable new insights into the climate history of Earth.
"At the moment, it is like the first page of a book. Up until now we just had an ambitious plan. Now we have all this remarkable data to pore over," Dr Ferraccioli.
AGAP was a flagship expedition for International Polar Year (IPY), a concerted effort by the science community to better understand both the Antarctic and the Arctic. IPY formally closes on Wednesday.
The mountains were named after a Russian geophysicist known as Grigoriy Gamburtsev. The presence of the range was first detected by a Soviet expedition in 1958.
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