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1. Encyclopedia of Lunar Science: Contribution of Surface Processes to the Lunar Exosphere

   https://doi.org/10.1007/978-3-319-05546-6  

   Dukes, Catherine A.; Johnson, Robert E. (April 2017, Encyclopedia of Lunar Science)

   The lunar exosphere is generated by a variety of processes: photodesorption from solar UV radiation (PSD), solar wind ion sputtering, meteoritic bombardment, radioactive decay, and thermal desorption. While remote or orbital temporal measurements provide in situ clues to source mechanisms, individual ejection processes are more easily and deeply investigated in laboratory experiments on returned Apollo samples and analogs, allowing quantitative comparisons at lunar-like pressures and temperature. The importance of laboratory experiments cannot be overemphasized, providing measurements of ejection probabilities relevant to exospheric formation, as well as metrics such as surface charge, surface composition and phase, and meteoritic-impact plume characterization. These parameters can be convolved to describe telescopic observations as well as phenomena observed at the lunar surface by orbital / lander measurements, providing ground truth for models of spatial and temporal variations in the exosphere. The following discussion of laboratory work pertinent to the generation of the lunar atmosphere is a starting point for those interested in laboratory simulations and is by no means an exhaustive review. 

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2. The reactivity of experimentally reduced lunar regolith simulants: Health implications for future crewed missions to the lunar surface

   https://doi.org/10.1111/maps.14228  

   Hendrix, Donald A; Catalano, Tristan; Nekvasil, Hanna; Glotch, Timothy D; Legett, Carey; Hurowitz, Joel A (June 2024, Meteoritics & Planetary Science)

   Abstract Crewed missions to the Moon may resume as early as 2026 with NASA's Artemis III mission, and lunar dust exposure/inhalation is a potentially serious health hazard that requires detailed study. Current dust exposure limits are based on Apollo‐era samples that spent decades in long‐term storage on Earth; their diminished reactivity may lead to underestimation of potential harm that could be caused by lunar dust exposure. In particular, lunar dust contains nanophase metallic iron grains, produced by “space weathering”; the reactivity of this unique component of lunar dust is not well understood. Herein, we employ a chemical reduction technique that exposes lunar simulants to heat and hydrogen gas to produce metallic iron particles on grain surfaces. We assess the capacity of these reduced lunar simulants to generate hydroxyl radical (OH*) when immersed in deionized (DI) water, simulated lung fluid (SLF), and artificial lysosomal fluid (ALF). Lunar simulant reduction produces surface‐adhered metallic iron “blebs” that resemble nanophase metallic iron particles found in lunar dust grains. Reduced samples generate ~5–100× greater concentrations of the oxidative OH* in DI water versus non‐reduced simulants, which we attribute to metallic iron. SLF and ALF appear to reduce measured OH*. The increase in observed OH* generation for reduced simulants implies high oxidative damage upon exposure to lunar dust. Low levels of OH* measured in SLF and ALF imply potential damage to proteins or quenching of OH* generation, respectively. Reduction of lunar dust simulants provides a quick cost‐effective approach to study dusty materials analogous to authentic lunar dust. 

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3. On the eruptive origins of lunar localized pyroclastic deposits

   https://doi.org/10.1016/j.epsl.2020.116426  

   Keske, Amber L.; Clarke, Amanda B.; Robinson, Mark S. (October 2020, Earth and Planetary Science Letters)
4. Anomalous ³³ S in the Lunar Mantle

   https://doi.org/10.1029/2022JE007597  

   Dottin, J. W.; Kim, S.‐T.; Wing, B.; Farquhar, J.; Shearer, C. (February 2023, Journal of Geophysical Research: Planets)

   Abstract The origin, evolution, and cycling of volatiles on the Moon are established by processes such as the giant moon forming impact, degassing of the lunar magma ocean, degassing during surface eruptions, and lunar surface gardening events. These processes typically induce mass‐dependent stable isotope fractionations. Mass‐independent fractionation of stable isotopes has yet to be demonstrated during events that release large volumes of gas on the moon and establish transient lunar atmospheres. We present quadruple sulfur isotope compositions of orange and black glass beads from drive tube 74002/1. The sulfur isotope and concentration data collected on the orange and black glasses confirm a role for magmatic sulfur loss during eruption. The Δ³³S value of the orange glasses is homogenous (Δ³³S = −0.029‰ ± 0.004‰, 2SE) and different from the isotopic composition of lunar basalts (Δ³³S = 0.002‰ ± 0.004‰, 2SE). We link the negative Δ³³S composition of the orange glasses to an anomalous sulfur source in the lunar mantle. The nature of this anomalous sulfur source remains unknown and is either linked to (a) an impactor that delivered anomalous sulfur after late accretion, (b) sulfur that was photochemically processed early during lunar evolution and was transported to the lunar mantle, or (c) a primitive sulfur component that survived mantle mixing. The examined black glass preserves a mass‐dependent Δ³³S composition (−0.008‰ ± 0.006‰, 2SE). The orange and black glasses are considered genetically related, but the discrepancy in Δ³³S composition among the two samples calls their relationship into question. 

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5. Lunar Infrastructure via Microscale Regolith Assembly

   https://doi.org/10.2514/6.2021-0148  

   Eckman, Elise; Peck, Mason A.; Napp, Nils (January 2021, AIAA 2021-0148 Session: Flight Systems and In-Space Infrastructure)

   null (Ed.)

   Multiscale Granular Stacking (MSGS) is a technology for assembling planetary-surface infrastructure from unprocessed regolith. The unprocessed grains serve directly as additive manufacturing feedstock in a process that exploits their natural variation in size and shape. With precise, single-grain scanning, computation, and packing, MSGS minimizes and potentially eliminates the need for adhesives, fluids, and other binders, saving the associated mass and energy. Preliminary calculations suggest that MSGS requires less mass transport and energy for construction than traditional terrestrial building methods, drastically reducing the reliance on earth resources for sustaining a deep-space human presence and long-term exploration goals. Constructing a desired structure may require stacking millions of grains which demands extensive computation. Packing solutions with many objects exist in the literature, e.g. some versions of the knapsack problem. However, micro- to macro-scale particle dry stacking itself has never been investigated, let alone in the context of space additive manufacturing. Modeling these fabrication process dynamics as a discrete-step linear system allows for tuning of parameters such as build speed, surface finish, and contour smoothing while providing the opportunity to leverage controls theory for determining system convergence, steady-state error, and overshoot of desired build height. This paper details attempts to bring multivariable control theory to bear on additive manufacturing by using feedback on overall build geometry, a technique proven to yield more accurate results than using feedback at the process level in traditional additive manufacturing. 

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