An enormous canyon never before seen by human eyes is buried beneath the icy surface of Greenland, according to scientists at NASA, the British Antarctic Survey and the University of Bristol, who used a variety of satellite imaging techniques to locate the previously unknown mega canyon.

With a length of at least 460 miles and a depth in some places of 2,600 feet, the scale of this buried canyon rivals the Grand Canyon and is home to an ancient river system.

The six-mile-wide mega canyon is believed to predate the ice sheet that has covered Greenland for that last several million years, according to the scientists, who published their find Thursday in the journal Science.

"One might assume that the landscape of the Earth has been fully explored and mapped," said Jonathan Bamber, professor of physical geography at the University of Bristol in the United Kingdom, and lead author of the study. "Our research shows there's still a lot left to discover."

Deep beneath Greenland's icy surface, the canyon meanders northward from Summet, the highest point in central Greenland, toward the Petermann Glacier on the northwest coast, according to LiveScience, which added that Bamber told them that the canyon may be even longer than what has been announced, but there is not enough data to prove it yet.

"It may actually go farther south," Bamber said.

To collect the data, Bamber teamed up with NASA to access information collected by the space agency's Operation IceBridge program, a six-year mission which is the largest airborne survey ever done on polar ice. One of the instruments used in IceBridge is capable of seeing through vast layers of ice to measure the thickness and shape of the bedrock below.

Researchers were able to measure the depth of the canyon by bouncing radio waves off the bedrock underneath the ice sheet. The longer it took for the waves to bounce back, the deeper the canyon went.

"A discovery of this nature shows that the Earth has not yet given up all its secrets," said David Vaughan of British Antarctic Survey in Cambridge. "A 750km canyon preserved under the ice for millions of years is a breathtaking find in itself, but this research is also important in furthering our understanding of Greenland's past. This area's ice sheet contributes to sea level rise and this work can help us put current changes in context."

The researchers believe the canyon plays a role in transporting sub-glacial meltwater to the edge of the ice sheet and ultimately into the ocean. Evidence suggests that before the ice sheet formed about 4 million years ago, the canyon provided a pathway for water to travel from Greenland's interior to its coast.

"Two things helped lead to this discovery," said Michael Studinger, IceBridge project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "It was the enormous amount of data collected by IceBridge and the work of combining it with other datasets into a Greenland-wide compilation of all existing data that makes this feature appear in front of our eyes."

"It is quite remarkable that a channel the size of the Grand Canyon is discovered in the 21st century below the Greenland ice sheet," said Studinger. "It shows how little we still know about the bedrock below large continental ice sheets."