We assess the geographic distribution and temporal variability of seasonal shadow at the lunar polar regions and explore its influence on surface water migration and deposition within known permanently shadowed regions (PSRs) in the modern era. At its largest expanse near the winter solstice, seasonally shadowed area more than doubles the permanently shadowed area at both poles. The growth and decay of polar shadow throughout the year enforce distinct seasonal patterns in the poleward migration of water as well as a cyclical variation in the polar surface hydration throughout the year if a continual source of water is assumed. The polar surface water abundance peaks near the hemispheric vernal equinox-significantly offset from the solstice where the seasonal trapping area is most expansive-due to the retention of seasonally trapped water. Owing to their low areal density, lower-latitude PSRs do not significantly hamper the poleward migration of water, enabling water to reach the high polar latitudes where cold trapping area is densest. We find that northern hemisphere PSRs accumulate more water per unit area than southern hemisphere PSRs and that this disparity is especially prominent beyond 85 degrees. The north/south asymmetry is attributed to differences in the hemispheric PSR size-frequency distributions; such differences enable unique north/south migration diffusivities, which favor more water reaching the high northern latitudes.

Incorporation of in situ resource utilization (ISRU) and the production of mission-critical consumables for propulsion, power, and life support into mission architectures can greatly reduce the mass, cost, and risk of missions, leading to a sustainable and affordable approach to human exploration beyond Earth. ISRU and its products can also greatly affect how other exploration systems are developed, including determining which technologies are important or enabling. Although the concept of lunar ISRU has existed for more than 40 years, the technologies and systems had not progressed much past simple laboratory proof-of-concept tests. With the release of the Vision for Space Exploration in 2004 with the goal of harnessing the Moon's resources, the National Aeronautics and Space Administration (NASA) initiated the ISRU project in the Exploration Technology Development Program (ETDP) to develop the technologies and systems needed to meet this goal. In the 5 years of work in the ISRU Project, significant advancements and accomplishments occurred in several important areas of lunar ISRU. Also, two analog field tests held in Hawaii in 2008 and 2010 demonstrated all the steps in ISRU capabilities required, along with the integration of ISRU products and hardware with propulsion, power, and cryogenic storage systems. This paper will review the scope of the ISRU Project in the ETDP, ISRU incorporation, development strategies used by the ISRU project, and ISRU development and test accomplishments over the 5 years of funded project activity. DOI: 10.1061/(ASCE)AS.1943-5525.0000208. (C) 2013 American Society of Civil Engineers.