In the coming decades, exploration of the lunar surface is likely to increase as multiple nations execute ambitious lunar exploration programs. Among several environmental effects of such activities, increasing traffic near and on the lunar surface will result in the injection of anthropogenic neutral gases into the lunar exosphere. The subsequent ionization of such anthropogenic neutrals in the lunar environment may contribute to and ultimately exceed the generation of 'native' lunar pickup ions, thereby altering the fundamental space plasma interaction with the Moon. To better understand these possible effects, we conducted plasma simulations of the solar wind interaction with the Moon in the presence of increasing ion production rates from an anthropogenic lunar exosphere. At ionization levels between 0.1 and 10 times the native lunar exospheric ion production rate, little to no changes to the solar wind interaction to the Moon are present; however, ionization levels of 100 and 1000 times the native rate result in significant mass loading of the solar wind and disruption of the present-day structure of the Moon's plasma environment. Comparing to the planned Artemis landings, which are likely to contribute only an additional X10% of the native lunar exospheric ion production rate, we conclude that the Artemis program will have little effect on the Moon's plasma environment. However, more frequent landings and/or continual outgassing from human settlements on the Moon in the more distant future are likely to fundamentally alter the lunar plasma environment. (c) 2024 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The lunar exosphere is an ensemble of multiple overlapping, noninteracting neutral distributions that reflect the primary physical processes acting on the lunar surface. While previous observations have detected and constrained the behavior of some species, many others have only circumstantial evidence or theoretical modeling suggesting their presence. Many species are so tenuous as to be unobservable by direct neutral sampling, yet in comparison, measurements in their ionized form provide a particularly sensitive method of detection. To better aid the interpretation of past measurements and planning of future observations, we present a model for the production of lunar pickup ions from the Moon consisting of two components: An analytic model for the distributions of 18 neutral species produced by various mechanisms and an analytic model for the ionization and subsequent acceleration of 20 exospheric and surface-sputtered pickup ion species. The dominant lunar pickup ions in the model are H2+ ${\mathrm{H}}_{2}{+}$, He+, CO+, Ar-40(+), Al+, Na+, K+, Si+, Ca+, and O+ with an asymmetric distribution favoring the positive interplanetary electric field hemisphere of the Moon. We compare the model predictions to statistically averaged pickup ion fluxes around the Moon as observed by the ARTEMIS spacecraft over the past decade. By filtering for interplanetary electric field-aligned, high-energy observations, we find that the pickup ion model lacks an additional source of heavy species. We suggest that a dense CO2 exosphere of 3 x 10(4) - 1 x 10(5) cm(-3) could account for the missing pickup ion flux as part of the recycling of solar wind carbon ions incident to the Moon.

The study of multiscale pickup ion phase-mixing in the lunar plasma wake with a hybrid model is the main subject of our investigation in this paper. Photoionization and charge exchange of protons with the lunar exosphere are the ionization processes included in our model. The computational model includes the self-consistent dynamics of the light (H+ or H-2(+) and He+), and heavy (Na+) pickup ions. The electrons are considered as a fluid. The lunar interior is considered as a weakly conducting body. In this paper we considered for the first time the cumulative effect of heavy neutrals in the lunar exosphere (e.g., Al, Ar), an effect which was simulated with one species of Na+ but with a tenfold increase in total production rates. We find that various species produce various types of plasma tail in the lunar plasma wake. Specifically, Na+ and He pickup ions form a cycloid-like tail, whereas the H+ or H-2(+) pickup ions form a tail with a high density core and saw-like periodic structures in the flank region. The length of these structures varies from 1.5 R-M to 3.3 R-M depending on the value of gyroradius for H+ or H-2(+) pickup ions. The light pickup ions produce more symmetrical jump in the density and magnetic field at the Mach cone which is mainly controlled by the conductivity of the interior, an effect previously unappreciated. Although other pickup ion species had little effect on the nature of the interaction of the Moon with the solar wind, the global structure of the lunar tail in these simulations appeared quite different when the H-2(+) production rate was high.

By analyzing the trajectories of ionized constituents of the lunar exosphere in time-varying electromagnetic fields, we can place constraints on the composition, structure, and dynamics of the lunar exosphere. Heavy ions travel slower than light ions in the same fields, so by observing the lag between field rotations and the response of ions from the lunar exosphere, we can place constraints on the composition of the ions. Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) provides an ideal platform to utilize such an analysis, since its two-probe vantage allows precise timing of the propagation of field discontinuities in the solar wind, and its sensitive plasma instruments can detect the ion response. We demonstrate the utility of this technique by using fully time-dependent charged particle tracing to analyze several minutes of ion observations taken by the two ARTEMIS probes similar to 3000-5000km above the dusk terminator on 25 January 2014. The observations from this time period allow us to reach several interesting conclusions. The ion production at altitudes of a few hundred kilometers above the sunlit surface of the Moon has an unexpectedly significant contribution from species with masses of 40amu or greater. The inferred distribution of the neutral source population has a large scale height, suggesting that micrometeorite impact vaporization and/or sputtering play an important role in the production of neutrals from the surface. Our observations also suggest an asymmetry in ion production, consistent with either a compositional variation in neutral vapor production or a local reduction in solar wind sputtering in magnetic regions of the surface.

We present latitude and longitude distributions of Na+ and K+ fluxes from the Moon derived from Kaguya low-energy ion data. Although the latitude distribution agrees with previous ground-based telescope observations, dawn-dusk asymmetry has been determined in the longitude distribution. Our model of the lunar surface abundance and yield of Na and K demonstrates that the abundance decreases to approximately 50% at dusk compared with that at dawn due to the emission of the exospheric particles assuming the ion fluxes observed by Kaguya are proportional to the yield. It is also implied that the surface abundance of Na and K need to be supplied during the night to explain the observed lunar exosphere with dawn-dusk asymmetry. We argue that the interplanetary dust as well as grain diffusion and migration/recycling of the exospheric particles may be major suppliers.

In this report we discuss the self-consistent dynamics of pickup ions in the solar wind flow around the lunar-like object. In our model the solar wind and pickup ions are considered as a particles, whereas the electrons, are described as a fluid. Inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. The Moon will be chosen as a basic object for our modeling. The current modeling shows that mass loading by pickup ions H+, H-2(+), He+, and Na+ may be very important in the global dynamics of the solar wind around the Moon. In our hybrid modeling we use exponential profiles for the exospheric components. The Moon is considered as a weakly conducting body. Special attention will be paid to comparing the modeling pickup ion velocity distribution with ARTEMIS observations. Our modeling shows an asymmetry of the Mach cone due to mass loading, the upstream flow density distribution and the magnetic field. The pickup ions form an asymmetrical plasma tails that may disturb the lunar plasma wake. (C) 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.

Observations of heavy ions of lunar origin give important information regarding lunar exospheric processes, especially with respect to exospheric particle abundance and composition. Electrostatic analyzers without a time-of-flight provide highly sensitive, absolute density detection but without mass discrimination. Here we place constraints on lunar ion species through inference of the average ion mass using such instruments. The technique is based on the plasma quasi-neutrality requirement, an independent electron density measurement, and the fact that electrostatic analyzers underestimate the ion density by the square root of the ion mass. Applied to a case of such observations by ARTEMIS in the terrestrial lobe reported by Poppe et al. (2012), our technique suggests an average mass of 28 amu for lunar pickup ions. This result, consistent with the lower limit of 24 amu derived in the Poppe et al. model, suggests that the observed ions were most likely Al+ and Si+. The technique is also refined and applied to a more complicated event with a series of heavy ion surges in the plasma sheet, to show the spatial and/or temporal dependence of the observed lunar ion species. The technique is particularly timely given the planned conjunctions and coordinated lunar studies by NASA's Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) and Lunar Atmosphere and Dust Environment Explorer missions.

The lunar exosphere is produced by a combination of processes including thermal desorption, micrometeoroid bombardment, internal gas release, photon-stimulated desorption, and charged-particle sputtering. Here we investigate an additional mechanism not previously considered for the Moon, namely the role that newly born ions from the exosphere itself play in sputtering additional neutrals from the lunar surface, known as self-sputtering. Our calculations suggest that this process may sputter neutrals into the lunar exosphere at a rate equal to or greater than charged-particle sputtering due to passage through the Earth's plasma sheet when spatially averaged over the lunar dayside, while locally, self-sputtering may equal or exceed solar wind charged-particle sputtering and micrometeoroid bombardment. We use known or modeled densities and distributions of exospheric neutrals, laboratory-derived values for the photoionization rates and neutral sputtering yields, and knowledge of the ambient electromagnetic environment at the Moon to derive estimates of the self-sputtered neutral flux. We present the spatial variation of the self-sputtered neutral flux and discuss the implications thereof.

In this report we discuss the self-consistent dynamics of pickup ions in the solar wind flow around the lunar-like object. In our model the solar wind and pickup ions are considered as a particles, whereas the electrons are described as a fluid. inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. The Moon will be chosen as a basic object for our modeling. The current modeling shows that mass loading by pickup ions Na+ and He+ may be very important in the global dynamics of the solar wind around the Moon. In our hybrid modeling we use exponential profiles for the exospheric components. The Moon is considered as a weakly conducting body. Special attention will be paid to comparing the modeling pickup ion velocity distribution with ARTEMIS observations. Our modeling shows an asymmetry of the Mach cone due to mass loading, the upstream flow density distribution and the magnetic field. The pickup ions form an asymmetrical plasma tails that may disturb the lunar plasma wake. (C) 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.