¹Francisca S. Paiva,^2,3Silvio Sinibaldi
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009132]
¹KU Leuven, Leuven, Belgium
²European Space Agency, Noordwijk, The Netherlands
³The Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

Recent detections of water ice in the permanently shadowed regions (PSRs) at the lunar poles have reignited scientific and commercial interest in the exploration of Earth’s closest neighbor. The frigid temperatures in PSRs operate as cold traps for volatiles and may represent large reservoirs of materials, including water ice and prebiotic organic molecules, delivered to the Earth-Moon system through meteorite or cometary impacts over billions of years (Crawford, 2006, https://doi.org/10.1017/s1473550406002990). Nonetheless, scientific investigations of lunar poles rely on the absence of extraneous volatiles introduced during lunar missions, which may hide pristine evidence of such materials. In the present work, we develop a numerical model for the transport of spacecraft exhaust volatiles on the Moon. Using ESA’s Argonaut missions as a case study, featuring a descent at the lunar South Pole, we apply this model to assess the potential impact of organic contamination from lunar landers on scientific research of lunar ice chemistry by tracing the migration of methane
molecules to the PSRs. Our simulation results suggest that approximately half of the released
molecules end up trapped in PSRs at the South or North poles within 7 lunar days, with their distribution dictated by interactions with the lunar surface. Moreover, cross-contamination between poles proves significant, as approximately
of molecules become trapped in the north polar region, despite only a limited fraction of these falling within the latitude limit of
defined for Category IIb in COSPAR Planetary Protection Policy.