A vast and previously unmapped gorge, 800 metres deep, has been found under ice in Greenland.
The canyon is 750 kilometres long and is said to be comparable in scale to parts of the Grand Canyon that is twice as deep – 1.6 kilometres – at its deepest.
The Greenland canyon is buried under deep ice.
Scientists used airborne data collected mainly by NASA and by scientists in Britain and Germany to piece together maps of the canyon.
Watch the video