Solar system exploration is that grand human endeavor which reaches out through interplanetary space to discover the nature and origins of the system of planets in which we live and to learn whether life exists beyond Earth. It is an international enterprise involving scientists, engineers, managers, politicians, and others, sometimes working together and sometimes in competition, to open new frontiers of knowledge. It has a proud past, a productive present, and an auspicious future. This survey was requested by the National Aeronautics and Space Administration (NASA) to determine the contemporary nature of solar system exploration and why it remains a compelling activity today. A broad survey of the state of knowledge was requested. In addition NASA asked for the identifcation of the top-level scientific questions to guide its ongoing program and a prioritized list of the most promising avenues for flight investigations and supporting ground-based activities.