The human impulse to explore new frontiers has taken us into space and to the deepest, most remote corners of our own planet. Stephen Sackur speaks to one woman who has done both. Kathy Sullivan was the first American woman to walk in space. She has just returned from a mission to the deepest point underneath the oceans. She is first and foremost a scientist; as we try to navigate our future, are we properly respecting the science? Show less