Surface Water at Lunar Magnetic Anomalies

The presence of water on the lunar surface has been confirmed by multiple Earth‐based and orbital observations. However, the origins of this water and the factors that control its stability at different latitudes are still debated. Magnetic anomalies on the Moon systematically reduce solar wind flux...

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Veröffentlicht in:Geophysical research letters 2019-12, Vol.46 (24), p.14318-14327
Hauptverfasser: Li, Shuai, Garrick‐Bethell, Ian
Format: Artikel
Sprache:eng
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Zusammenfassung:The presence of water on the lunar surface has been confirmed by multiple Earth‐based and orbital observations. However, the origins of this water and the factors that control its stability at different latitudes are still debated. Magnetic anomalies on the Moon systematically reduce solar wind flux while locally keeping other confounding variables constant, which provides a natural laboratory for understanding the contribution of solar wind to lunar surface water. We find that water mapped with Moon Mineralogy Mapper data exhibit strong suppressions at magnetic anomalies, indicating that reduced solar wind flux prevents the formation of water. Our results support the hypothesis that the solar wind contributes significantly to the presence of the lunar surface water. Future missions and studies focusing on how magnetic fields affect water production can provide essential clues about how surface water is formed on the Moon and other airless bodies. Plain Language Summary The presence of water and/or hydroxyl molecules on the Moon has been confirmed by multiple observations. However, the origins of the lunar surface water are still unknown. The water may arise from three possible origins: solar wind, impacts, and the lunar interior. Lunar magnetic anomalies provide a natural laboratory to assess which of the three sources may dominate. Strong magnetic fields can significantly reduce the energy and flux of solar wind particles reaching the surface while keeping other conditions unchanged, such as temperature and UV photon flux. In this study, we examined water maps derived from orbital data at magnetic anomalies across the lunar surface. We confirmed that the water content at anomalies is much lower than the surrounding regions, providing direct evidence that solar wind contributes substantially to the lunar surface water production. Future missions and studies may help quantify how magnetic fields affect the formation rate of water by solar wind implantation. These results may be important for understanding solar wind water formation on other airless bodies. Key Points The spatial correlation between 3‐μm water absorption features from Moon Mineralogy Mapper (M3) data and lunar lithospheric magnetic fields is assessed Magnetic anomalies exhibit strong water suppressions that are not artifacts of thermal corrections Strong suppression of water features at magnetic anomalies suggests that lunar surface water mostly originates from solar wind implantation
ISSN:0094-8276
1944-8007
DOI:10.1029/2019GL084890