New Study Reveals Scarcity of Water in Moon's Permanently Shadowed Regions

A recent study led by Shuai Li, a planetary geologist at the University of Hawaii at Manoa, indicates that the amount of water ice in the Moon's permanently shadowed regions (PSRs) may be significantly lower than previously anticipated. The research, published in the journal *Science Advances*, utilized data from NASA's ShadowCam instrument aboard South Korea's Danuri lunar orbiter, launched in 2022. The study suggests that many of the Moon's darkest craters, particularly those at the lunar south pole, may contain little to no surface ice, with estimates indicating that water could constitute less than 20-30% of the material in these areas.

NASA's ShadowCam on Danuri suggests less water ice in lunar polar cratersScientific American

The quest for lunar water has evolved since the Apollo 11 mission, which returned nearly 50 pounds of lunar material that initially led scientists to conclude the Moon was devoid of water. However, the discovery of water traces by the U.S. Clementine spacecraft in the 1990s reignited interest in the Moon's water content, particularly in PSRs where sunlight never reaches. Despite these earlier findings, the current study raises questions about the actual abundance of water ice on the Moon's surface.

Scientific AmericanNASA's ShadowCam on Danuri suggests less water ice in lunar polar craters

The research team analyzed high-resolution images from ShadowCam, which can detect ice through light scattering and reflection. However, the instrument has a detection limit, meaning it cannot identify ice if it constitutes less than 20-30% of the total material. The absence of detectable ice in the analyzed images led the researchers to conclude that the water content is below this threshold, although they acknowledge the possibility of ice existing beneath the surface or being obscured by other materials.

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The findings have significant implications for future lunar missions, particularly as NASA considers the lunar south pole as a primary landing site for crewed missions. David Kring, director of a lunar science research center, emphasized the need for direct exploration to obtain more definitive answers about the Moon's water resources. He stated, "To get a more definitive answer, humans and robots must directly explore the lunar surface."

NASA's ShadowCam on Danuri suggests less water ice in lunar polar cratersScientific American

While the study provides valuable insights, some experts argue that orbital measurements alone cannot fully address the complexities of lunar water distribution. Kring noted that "orbital measurements... can provide broad regional surveys, but oftentimes what you’re looking for can only be addressed by in situ, ‘boots on the ground’ exploration activities." This highlights the necessity for future missions to include both robotic and human exploration to better understand the Moon's water resources.

NASA's ShadowCam on Danuri suggests less water ice in lunar polar craters

• “This is a significant study that provides information about the vast PSR areas,” — David Kring, Director, Lunar Science Research Center

NASA's ShadowCam on Danuri suggests less water ice in lunar polar craters

• “The sooner that we get robotic and human assets on the lunar surface to investigate this particular issue, the sooner we’ll have some definitive answers.” — David Kring, Director, Lunar Science Research Center

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The study underscores the ongoing challenges in determining the availability of water on the Moon, a critical resource for future exploration and potential lunar bases.

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