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In fulfilling the National Aeronautics and Space Administration's (NASA) responsibility to encourage the fullest commercial use of space the Space Product Development (SPD) Program, within the Microgravity Research Program Office (MRPO) located at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, is managing an organization of Commercial Space Centers (CSC's) that have successfully employed methods for encouraging private industries to exploit the benefits of space-based research. Unique research opportunities of the space environment are being made available to private industry in an effort to develop new, competitive products; create jobs; and enhance the country's quality of life. Over 200 commercial research activities have been conducted in space by the CSC's and their industrial partners during the last several years. The success of this research is evidenced by the increasing amount of industrial participation in commercial microgravity research and the potential products nearing marketability. 相似文献
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Recent models for the origin of Jupiter indicate that the Galilean satellites were mostly derived from largely unprocessed solar nebula solids and planetesimals. In the jovian subnebula the solids that built Europa were first heated and then cooled, but the major effect was most likely partial or total devolatilization, and less likely to have been wholesale thermochemical reprocessing of rock + metal compositions (e.g., oxidation of Fe and hydration of silicates). Ocean formation and substantial alteration of interior rock by accreted water and ice would occur during and after accretion, but none of the formation models predicts or implies accretion of sulfates. Europa's primordial ocean was most likely sulfidic. After accretion and later radiogenic and tidal heating, the primordial ocean would have interacted hydrothermally with subjacent rock. It has been hypothesized that sulfides could be converted to sulfates if sufficient hydrogen was lost to space, but pressure effects and the impermeability of serpentinite imply that extraction of sulfate from thoroughly altered Europa-rock would have been inefficient (if indeed Mg sulfates formed at all). Permissive physical limits on the extent of alteration limit the sulfate concentration of Europa's evolved ocean to 10% by weight MgSO(4) or equivalent. Later oxidation of the deep interior of Europa may have also occurred because of water released by the breakdown of hydrated silicates, ultimately yielding S magma and/or SO(2) gas. Geological and astrobiological implications are considered. 相似文献
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