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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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Kinetic Particle Simulations of Plasma Charging at Lunar Craters Under Severe Conditions
This paper presents fully kinetic particle simulations of plasma charging at lunar craters with the presence of lunar lander modules using the recently developed Parallel Immersed-Finite-Element Particle-in-Cell (PIFE-PIC) code. The computation model explicitly includes the lunar regolith layer on top of the lunar bedrock, taking into account the regolith layer thickness and permittivity as well as the lunar lander module in the simulation domain, resolving a nontrivial surface terrain or lunar lander configuration. Simulations were carried out to study the lunar surface and lunar lander module charging near craters at the lunar terminator region under mean and severe plasma environments. The lunar module’s position is also investigated to see its effect on the plasma charging relative to the craters. Differential surface charging was clearly resolved by the simulations. For the charging of a lunar lander module made of conducting materials, the results show a near-uniform potential close to that of its surrounding environment and moderate levels of local electric fields. Additionally, the risks associated with charging and discharging increase significantly under a more severe plasma charging environment as shown in the severe plasma environment cases.
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- PAR ID:
- 10436164
- Publisher / Repository:
- ARC
- Date Published:
- Journal Name:
- Journal of Spacecraft and Rockets
- Volume:
- 60
- Issue:
- 4
- ISSN:
- 0022-4650
- Page Range / eLocation ID:
- 1176 to 1187
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.2514/1.A35622
