NASA's Quest for Lunar Water: Exploring the Moon's South Pole

NASA is collaborating with the Japan Aerospace Exploration Agency (JAXA) and the Indian Space Research Organisation (ISRO) on the Lunar Polar Exploration (LUPEX) mission, aimed at locating ice on the Moon. Central to this effort is NASA's Neutron Spectrometer System (NSS), a water-detecting instrument designed to identify hydrogen concentrations indicative of water ice beneath the lunar surface. The NSS will be installed on a lunar rover scheduled to arrive at the Moon no earlier than 2028. This mission is part of NASA's broader strategy to establish a sustainable human presence on the Moon, utilizing local resources rather than relying solely on supplies from Earth.

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Water is essential for future lunar exploration, serving as a source of breathable air and rocket fuel. The Moon's water is primarily found as molecules within lunar regolith, with potential ice deposits located beneath the surface, particularly at the lunar South Pole. Rick Elphic, NSS lead at NASA’s Ames Research Center, emphasized the need for ground missions to understand the distribution of lunar ice at various scales, stating, “The only way to understand the ‘where’ and ‘how much’ of lunar ice is by exploring on the surface at these scales.”

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The NSS employs a gas proportional counter that detects neutrons interacting with hydrogen atoms in the lunar soil. This interaction results in a measurable deficit of medium-energy neutrons, indicating the presence of hydrogen. The NSS can infer hydrogen presence up to three feet underground, providing critical data for future lunar missions. NASA plans to deploy multiple NSS instruments across various missions, including the upcoming VIPER (Volatiles Investigating Polar Exploration Rover) mission and the MoonRanger micro rover developed by Carnegie Mellon University.

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Despite NASA's optimistic outlook, recent studies have raised questions about the availability of water on the Moon. Research conducted by astronomers from the University of Hawaii, utilizing NASA's ShadowCam aboard the Korea Pathfinder Lunar Orbiter, found no evidence of water ice in permanently shadowed regions of the Moon. These areas, which never receive sunlight, were previously thought to harbor significant ice deposits. The study suggests that while previous missions indicated the presence of water ice, the actual amounts may be less than anticipated, with some estimates suggesting only about 10% water ice levels, which would be undetectable by current methods.

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As NASA continues its efforts to locate and utilize lunar water, upcoming missions will aim to refine detection techniques, potentially lowering the threshold for identifying ice to as little as 1% in surface mixtures. The ongoing investigation into the Moon's water resources is crucial for planning sustainable human activities on the lunar surface.

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• “There is currently a gap in our understanding of how lunar ice is distributed at small scales, from 10s of centimeters up to 10s of kilometers,” — Rick Elphic, NSS Lead, NASA Ames Research Center

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• “The three upcoming NSS rover expeditions will tell us what kinds of places on the Moon are most likely to host ice,” — Rick Elphic, NSS Lead, NASA Ames Research Center

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This comprehensive approach to lunar exploration underscores the complexities and challenges of establishing a human presence on the Moon, highlighting the need for continued research and collaboration among international space agencies.

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