A journey to the bottom of the world in search of the purest thing.
A dozen or so of us were packed into the beluga-shaped DC-3, snorting oxygen through plastic medical tubes to make up for the thin, 20,000-foot air in the unpressurized cabin. The Antarctic plateau slid beneath us 10,000 feet below, though without the visual reference of trees, mountains, buildings or roads, it appeared to be close enough for a sharp tip of the wing to scratch the surface of the snow. Far off in the distance the horizon hinted at the curvature of the earth.