Explorers of earth, air, ocean, and space share the extreme challenges and rewards of universal exploration. Guest appearance by astronaut Catherine (Cady) Coleman '83, currently aboard the International Space Station.   * Maria T. Zuber, E.A. Griswold Professor of Geophysics; Head, Department of Earth, Atmospheric and Planetary Sciences, MIT * Steven W. Squyres, Goldwin Smith Professor of Astronomy, Cornell University * Buzz Aldrin ScD '63, Astronaut * James G. Bellingham '84 SM '84 PhD '88, Chief Technologist, Autonomous Ocean Sampling Network Program, Monterey Bay Aquarium Research Institute