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The Biology of Low Atmospheric Pressure – Implications for Exploration Mission Design and Advanced Life Support.   R.J. Ferl1 A-L. Paul1, A.C. Schuerger2, M.A. Dixon3, 1Dept of Horticultural Sciences, University of Florida, Gainesville, FL. 2Dept Plant Pathology, U. of Florida, SLS Lab, KSC, FL,  3Dept Environmental Biology, U. of Guelph, Guelph, Ontario.

   Atmospheric pressure is a variable that has been often manipulated in the trade space surrounding the design and engineering of space exploration vehicles and extraterrestrial habitats. Low pressures were used to reduce structural engineering and launch mass throughout the early human space program, and low pressures will certainly be considered in future concepts for the same reasons. Fundamental understanding of the biological impact of low pressure environments is therefore critical for the successful consideration of this variable. This is particularly important when considering Advanced Life Support (ALS) systems with potentially complex biological systems.

   We have identified the molecular genetic responses central to the initial exposure of Arabidopsis to hypobaric stress (Paul et al. 2004, Plant Physiol). Less than half of the genes induced by hypobaria are induced by hypoxia, establishing that response to hypobaria is unique and is more complex than just an adaptation to low of oxygen. In addition, the suites of genes induced by hypobaria confirm that water movement is a paramount issue. Current experiments examine gene expression profiles in response to a wide variety of pressures, ranging from slight hypobaria at 75 kPa (such as experienced in the shuttle during EVA) to extreme hypobaria at 0.7 kPa (Mars surface equivalent).  Results indicate that even small changes in atmospheric pressure have attendant biological consequences deserving consideration during the concept and design of vehicles and habitats. Moreover, the range of pressures in which plants can successfully adapt suggests that very low pressures can be considered for plant-specific habitats.

   Supported by NASA grant NNA04CC6