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— What regional and global observations are required to assess the present condi- 

 tion and to predict future states of the world's ecosystems? 



• Exobiology 



— What factors are required for the generation and evolution of life, and are these 

 factors unique to Earth? 



— Did life ever evolve on Mars and, if so, what happened to this life and what 

 are the implications for life on Earth? 



— How do astrophysical processes — such as solar activity and comet or asteroid 

 impacts — influence the distribution of life on evolving, habitable planets in 

 the cosmos? 



The goal of CELSS research is a system that regenerates food, air, and water for 

 crews on long-duration space flights. Several technologies may be considered for 

 recycling air and water in a closed system, but biological processes must synthesize 

 the complex materials needed to sustain human life. The CELSS Program has 

 begun testing "Breadboard," a pilot-scale biomass production chamber designed to 

 help develop a bioregenerative life support system. The research associated with 

 this effort and related programs extends from investigations of plant photosynthetic 

 processes to the physics and chemistry of supercritical wet oxidation of wastes. The 

 Breadboard Project will provide essential information on the stability and reliability 

 of bioregenerative life support systems. It remains an open question whether such 

 systems will flourish in space. 



Activities of the Biospherics Research Program are central to the Mission to Planet 

 Earth. They proceed from the recognition that biological processes have shaped the 

 chemical history of this planet. Interactions between the atmosphere and biosphere 

 vary over time, and the record of these changes preserved in sedimentary rocks has 

 been studied intensively to gain an understanding of the origin and evolution of life 

 on Earth. Recently, the pace of change has accelerated. Human activities, including 

 fossil fuel combustion, land use changes, and applications of novel industrial chem- 

 icals, have increased the concentrations of greenhouse gases and other atmospheric 

 constituents markedly. A workable, descriptive theory of the biosphere is needed to 

 understand the causes and consequences of these alterations. Environmental and 

 biological data must be collected on an unprecedented worldwide scale to provide 

 the basis for developing such a theory. Space capabilities are essential to this effort 

 because of the global view they afford and their increasing ability to sense surface 

 and atmospheric conditions remotely. 



The questions posed by exobiologists are scientific iterations of queries long pon- 

 dered by humankind, such as: Are we alone in the universe? How and where did 

 life begin? Robotic probes followed by human missions to Mars, which is near the 

 limits of our flight technology, will provide unique opportunities to obtain some 

 answers. 



( urrent knowledge suggests that water, a prime requisite for life, once coursed 



a< ross the surface of Mars and that the early environment on the planet was similar 



