MarkWhittington writes: Water ice believed by scientists to reside at the lunar poles is the key to opening up the solar system to human activity. The water could help sustain a lunar settlement. It could also be refined into rocket fuel, not only to sustain travel to and from the moon but to make it a refueling stop for spacecraft headed deeper into the solar system. A recent MIT study suggested that lunar fuel would simplify NASA's Journey to Mars. Lunar scientist Paul Spudis, writing in Air and Space Magazine, pondered the next step in determining the extent and composition of the lunar ice. Spudis' idea is to deploy several dozen impact probes across one of the lunar polar regions.