The search for life in the solar system

The purpose of this account is to review the search extraterrestrial life in the solar system in the light present knowledge of the physical state of the . It is being written on the eve of the launch (August 1975) by the U.S. of two Viking spacecraft to . These unmanned spacecraft, each consisting of orbiter and an instrumented lander, are to perform first biological exploration of another planet. Viking mission, if successful, will answer. of the questions posed in this paper. Furthermore, Mars is the most plausible extraterrestrial of life in the solar system, the Viking results likely to have a strong influence on future of this kind.