Life on other planets in the solar system (with emphasis on Mars) will be investigated by full exploitation of space technology which will allow both remote (orbiter) and direct (lander) observations of the planetary atmosphere, surface, and subsurface. Certain characteristics of terrestrial life, such as growth and reproduction, provide a basis for relatively simple experiments which may be used on early missions to detect the existence of life on Mars. Later missions will provide extensive automatic laboratory capabilities for analyzing many samples taken from various depths and locations. Because of the hypothetical nature of current experiment designs, it is likely that visual observations of the planet will be required. Many technical problems are involved in storing and transmitting the large amounts of data over planetary distances. Such visual observations might very well be crucial in interpreting results from other experiments. Critical to all exploration of the Moon and planets are the requirements to: (1) prevent contamination of the environment with Earth organisms and preserve the existing conditions of the planet for biological exploration; (2) provide strict quarantine for anything returned to Earth from the Moon and planets. The biological exploration of Mars is a scientific undertaking of the greatest significance. Its realization will be a major milestone in the history of human achievement. The characterization of life, if present, and study of the evolutionary processes involved and their relationship to the evolution of terrestrial life would have a great scientific and philosophical impact. What is at stake is nothing less than knowledge of our place in nature. Extended Earth orbital flights with subhuman specimens will be used to determine the effects on Earth organisms of prolonged weightlessness, radiation, and removal from the influence of the Earth’s rotation. Such flights of biosatellites and other suitable spacecraft are expected to: (1) establish biological specifications for extending the duration of manned space flight; (2) provide a flexible means of testing unforeseen contingencies, thus providing an effective biological backup for manned missions; (3) yield experimental data more rapidly by virtue of the greater number and expendability of subjects; (4) anticipate possible delayed effects appearing in later life or in subsequent generations, through use of animal subjects with more rapid development and aging; (5) develop and test new physiological instrumentation techniques, surgical preparations, prophylactic techniques, and therapeutic procedures which are not possible on human subjects; and (6) provide a broad background of experience and data which will permit more accurate interpretations of observed effects of space flight on living organisms, including man. chapter 2 _Exobiology_