'Impact crater' hides under Greenland ice
What looks to be a large impact crater has been identified beneath the Greenland ice sheet.
The 31km-wide depression came to light when scientists examined radar images of the island's bedrock.
Investigations suggest the feature was probably dug out by a 1.5km-wide iron asteroid sometime between about 12,000 and three million years ago. Dr Iain McDonald, from Cardiff University, UK, is part of the discovery team. He spoke with our science correspondent Jonathan Amos.