In Greenland, but no one's ever seen it
                                
                                
                                    (Newser) -
                                    Scientists have—totally by accident—come across a hidden canyon that dwarfs the Grand one, the  BBC  reports. The researchers were using radar to map out Greenland's bedrock when they stumbled upon the 2,625-foot deep feature, which, at 500 miles, is longer than the Grand Canyon's 277...