His first experience of the polar regions was as third officer on Captain Robert Falcon Scott's Discovery Expedition, 1901–04, from which he was sent home early on health grounds. Determined to do better, he returned to Antarctica in 1907 as leader of the Nimrod Expedition. In January 1909, he and three companions made a southern march. They went to the farthest South latitude anyone had reached, at 88° 23' S, 97 geographical miles (112 statute miles, 180 km) from the South Pole. This was by far the closest to the pole in exploration history up to that time. For this achievement, Shackleton was knighted by Edward VII on his return home.