From Sarah Griffiths on Dailymail: "A 466 mile-long chasm on the same scale as parts of the Grand Canyon has been discovered beneath the Greenland ice sheet. The canyon, which is as deep as 800 metres in places, is thought to predate the ice sheet, which has itself been around for millions of years. It has the characteristics of a meandering river channel, although it dwarfs the UK’s largest river, the Severn, which is less than half the length and far more shallow. The canyon was found after scientists analysed radar signals collected by Nasa and researchers from the UK and Germany over several decades. At certain frequencies, ice is transparent to radio waves which can bounce off the bedrock underneath, according to a group of international researchers who published their findings in the journal Science. By analysing all the radar data the team discovered a continuous bedrock canyon that extends from the centre of the island and ends at its northern extremity in a deep fjord connecting to the Arctic ocean. Professor Jonathan Bamber, of Bristol University’s School of Geographical Sciences, said: 'With Google Streetview available for many cities around the world and digital maps for everything from population density to happiness one might assume that the landscape of the Earth has been fully explored and mapped. 'Our research shows there’s still a lot left to discover.' The researchers believe the canyon plays an important role in transporting sub-glacial meltwater produced at the bed from the interior to the edge of the ice sheet and ultimately into the ocean. Even before the presence of the ice sheet, going back at least four million years, the evidence suggests the canyon provided a pathway for water from the interior to the coast. Professor David Vaughan, ice2sea co-ordinator based at the British Antarctic Survey in Cambridge said: 'A discovery of this nature shows that the Earth has not yet given up all its secrets. '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.' Some of the data used in the study came from Nasa’s Operation IceBridge, which is a six-year mission and the largest airborne survey of Earth’s polar ice ever flown. Michael Studinger, a scientist working on the project based at Nasa Goddard Space Flight Centre said: 'Two things helped lead to this discovery. '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 750km-long channel the size of parts of the Grand Canyon is discovered in the 21st century below the Greenland Ice Sheet. 'It shows how little we still know about the bedrock below large continental ice sheets.'"