Exobiology 



development of the chemistry of life from 

 simple components of atmospheres, oceans, and 

 crustal rocks, to complex precursors, and to 

 cellular life forms; 3) Early Evolution of Life: 

 Biological evolution from the first organisms to 

 multicellular species and the relationship of 

 biological evolution to planetary evolution; 

 4) Evolution of Advanced Life: The emergence 

 of advanced life forms as influenced by 

 planetary or astrophysical phenomena. Two 

 additional components support these epochal 

 program components: 5) Solar System 

 Exploration and 6) Search for Extraterrestrial 

 Intelligence (SETI). The former carries the search 

 for evidence of life or its chemical precursors to 

 other bodies in the solar system with 

 spaceborne instruments and experiments; the 

 latter scans the skies with ground-based 

 radiotelescopes for signals produced by 

 technological civilizations in the galaxy. 



Exobiology and NASA's 

 Charter 



Taken In/ Viking Orbiter 1, this photograph of the Martian sur- 

 face shows a small channel system. Tlw channel, about 2.5 

 kilometers in width, has flmo features along its length and tribu- 

 taries that join the main channel. This and similar channels on 

 Mars suggest that water erosion may have occurred during a 

 warmer and wetter epoch in the planet's history. 



Among all Federal agencies, NASA is uniquely 

 chartered to explore the matter that exists and 

 the processes that occur in space within the 



solar system and beyond. The present understanding of biology and the natural 

 history of life on Earth leads to the conclusion that life originates and evolves on 

 planets and that biological evolution is subject to the vicissitudes of planetary and 

 solar system evolution. For these reasons, unparalleled opportunities to contribute 

 to the program's goal are embodied in the missions and projects associated with 

 NASA's exploration of space; the rationale for conducting the Exobiology Program 

 in NASA has been and continues to be firmly rooted in the Agency's charter. 



Scientific Goals and Objectives and 

 Strategies for Achievement 



Results of research supported by NASA's Exobiology Program show that water and 

 the prebiotic organic compounds believed to have been required as the building 

 blocks of the chemical precursors to living systems are widespread in the solar 

 system and beyond. The ubiquity of these compounds forms the basis for the 

 hypothesis that the origin of life is inevitable throughout the cosmos wherever 

 these ingredients occur and suitable planetary conditions exist. Given the enormity 

 of the observable universe, a prediction originating from this hypothesis is that 

 extraterrestrial life is widespread. 



Testing the theory that life is a natural consequence of the physical and chemical 

 processes engendered by the evolution of the cosmos requires a broadly based, 



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