Rocket Exhaust Derived Surface Water Migration at Lunar Landing Sites

Abstract Volatiles, especially water, are at the center of modern lunar explorations. They have various sources, including volcanism, asteroid/comet impacts, and Earth/solar wind implantations. However, due to the lack of in situ data, it has not been widely recognized that artificial activities, especially rocket exhaust, could significantly impact volatile behaviors on the Moon. Artificial impact becomes even more severe when the global community is marching toward the lunar south pole. Any artificially released volatiles could migrate to the cold traps in lunar polar regions, causing irreversible contamination for future explorations. The recent Chang'e‐5 and 6 landers could conduct novel direct measurements of surface volatile migration, as they carried spectrometers covering water absorption wavelength, and landing cameras that can monitor rocket plume‐regolith interactions. Based on their unprecedented data and quantitative water diffusion simulations, we propose an injection and release model of water on the lunar surface induced by rocket plumes. Our results depict the migration of lunar volatiles on the lunar surface on a fine scale, showing their resilience in a vacuum and hot environment by adhering to lunar soil regolith. We suggest that planetary protection must be considered for future explorations, especially those toward polar regions, from rocket exhaust until its effects can be mitigated.