For someone known for reaching Earth’s most geographically inaccessible places, Ross Turner seems remarkably at home in the still, slightly trapped air of the Royal Geographical Society in London. The place is deserted but full of ghosts: Shackleton’s Burberry helmet lurks in the collection and maps of a 17th-century world hang in the hallway. Alongside his identical twin, Hugo, who joins us on speakerphone from the Lake District, Turner is drawing on this legacy: The pair are professional adventurers, diving deep and roaming wide, rowing across the Atlantic and climbing Mt. Elbrus, Europe’s tallest mountain.
The 34-year-old brothers—who have the old-fashioned manners expected, somehow, of explorers—have spent the past decade on death-defying missions with modern preoccupati...