The Moon encountered an extreme space weather event (NOAA G5 class) on 10 May 2024, caused by a series of coronal mass ejections (CMEs). Chandra's Atmospheric Composition Explorer-2 (CHACE-2), a neutral gas mass spectrometer on board Chandrayaan-2 orbiter, made in situ observations of the lunar exosphere during this period. Observations show an increase in total pressure around the arrival time of the CME impact on the Moon. The corresponding total number densities derived from these observations show an enhancement in the total number densities by more than an order of magnitude. The increase in lunar exospheric number densities by a factor > 10, due to the solar wind ion sputter process, is consistent with earlier theoretical modeling. This is the first observational confirmation of the enhancement in lunar exospheric densities during a CME impact.

This study addresses a critical issue faced in harsh desert environments characterized by intense sunlight and dusty conditions, which pose significant challenges for applications ranging from solar panels and optical devices to architectural surfaces. In response, we have developed a silica coating that may offer a solution to these environmental challenges. The silica coating exhibits excellent anti-reflective properties, drastically reducing the amount of sunlight reflected from the coated surface and thereby enhancing photon absorption. This study examines the controlled tuning of optical and morphological properties in silica thin films, fabricated through reactive RF magnetron sputtering of an SiO2 target, using various oxygen-to-argon flow ratios [r(O2)=O2/Ar]. Empirical properties of the coatings were systematically examined and demonstrated to be finely tunable by adjusting r(O2). Additionally, surface morphology, as assessed by average roughness (Ra) measurements, was found to be strongly influenced by the oxygen concentration during deposition. Hydrophilicity of the silica coatings was assessed using contact angle measurements, demonstrating that the oxygen content in the films plays a significant role in influencing their hydrophilic properties. Furthermore, micromechanical properties of these silica coatings right after sputtering deposition and those exposed to outdoor conditions were systematically evaluated using Vickers indentation, showing, on one hand, that the hardness of the silica coatings can be regulated by adjusting the oxygen levels introduced during the deposition process, and on the other hand, a high mechanical stability of these silica even after 24 months of outdoor exposure in desert environments. Finally, this study also highlights that dust accumulation on the surface of these silica coatings is inversely proportional to the oxygen content into the films, demonstrating the coatings' self-cleaning properties. The hydrophobicity of the deposited silica thin films further contributes to their self-cleaning capabilities, making them particularly valuable in enhancing the performance of photovoltaic modules, especially in desert environments where dust accumulation can significantly impact efficiency. This multifaceted approach not only improves optical and mechanical properties but also offers a sustainable solution for maintaining the efficiency of solar panels and other devices in challenging environmental conditions.

Metallic ions are commonly found in the cis-lunar environment, primarily produced through the neutral lunar exosphere. They become prevalent species of lunar pickup ions as the Moon moves through the solar wind upstream, magnetosheath, and magnetotail. Extensive studies on the composition of lunar pickup ions from the Lunar Atmosphere and Dust Environment Explorer and THEMIS-ARTEMIS missions have revealed the significant presence of ions with around 28 and 40 amu near the Moon, which are later identified as metallic species such as Al+, Si+ and K+ ions. However, while these studies have provided valuable insights, the abundance of metallic ions and their variations with the Moon's location and solar activity has yet to be understood. This study calculates the production and ionization rates of metallic ions based on in-situ THEMIS-ARTEMIS observations. Our analysis indicates that the magnetosphere effectively reduces the production of metallic neutrals and ions due to the reduction of ionization and sputtering rates. The statistical analysis of the 12-year data set further shows that the lunar pickup ion fluxes are not heavily reliant on solar activity, and the median values remain relatively consistent over time. Therefore, the source rates of metallic pickup ions are associated with the location of the Moon rather than being dependent on solar activity. The outflow rates of heavy ion species from the Moon are comparable with the molecular and metallic ion rates from Earth's ionosphere, suggesting their essential roles in the dynamics of heavy ions in Earth's terrestrial environment.

Sputtering of lunar regolith by solar-wind protons and heavy ions with kinetic energies of about 1 keV/amu is an important erosive process that affects the lunar surface and exosphere. It plays an important role in changing the chemical composition and thickness of the surface layer, and in introducing material into the exosphere. Kinetic sputtering is well modeled and understood, hilt understanding of Mechanisms of Potential sputtering has lagged behind. In this study we differentiate the contributions of potenti sputtering from the standard (kinetic) sputtering in changing the chemical Composition and erosion rate of the lunar surface. Also we study the con: tribution of potential sputtering in developing the lunar exosphere. Our results show that potential sputtering enhances the total characteristic sputtering erosion rate by about 44%, and reduces sputtering time scales by the same amount. Potential sputtering also introduces more material into the lunar exosphere.

We use a laboratory facility to study the sputtering properties of centimeter-thick porous water ice subjected to the bombardment of ions and electrons to better understand the formation of exospheres of the icy moons of Jupiter. Our ice samples are as similar as possible to the expected moon surfaces but surface charging of the samples during ion irradiation may distort the experimental results. We therefore monitor the time scales for charging and discharging of the samples when subjected to a beam of ions. These experiments allow us to derive an electric conductivity of deep porous ice layers. The results imply that electron irradiation and sputtering play a non-negligible role for certain plasma conditions at the icy moons of Jupiter. The observed ion sputtering yields from our ice-samples are similar to previous experiments where compact ice films were sputtered off a micro-balance. (C) 2016 Elsevier Ltd. All rights reserved.

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.

Observation of the lunar exosphere is a tool for remote sensing of the surface properties. The sources of this exosphere are related to the interactions of the lunar surface with the solar radiation, with the solar wind or Earth's magnetospheric plasma, and with the interplanetary dust and meteorites. In fact, the exospheric particles are continuously created and subsequently lost in the interplanetary space, photo-ionized or re-adsorbed by the surface. Eventually, the estimation of the surface composition is not possible without the knowledge of the active release mechanisms. The relative weight of the different release processes of the various atoms, ions and molecules from the surface is still an open debate. Investigation of the Moon's release processes and interaction with the near-Earth environment is of crucial importance for both determining the relative process release contribution and understanding the surface evolution of other airless bodies, like Mercury and the giant planets' moons. In this work, an attempt to analyze the processes that take place on the surface of these small airless bodies, as a result of their exposure to the space environment, has been realized by means of the MonteCarlo Environment Simulation Tool (EST), applied to the Moon. The model results show that the different release processes can be identified by analysing the exospheric energy distribution. Finally, the instrument concept of the Analizzatore Lunare di ENA (ALENA), part of theMAGIA payload and specifically designed for detecting the high-energy particles released from the lunar surface is presented.

We report preliminary results on sputtering of a lunar regolith simulant at room temperature by singly and multiply charged solar wind ions using quadrupole and time-of-flight (TOF) mass spectrometry approaches. Sputtering of the lunar regolith by solar-wind heavy ions may be an important particle source that contributes to the composition of the lunar exosphere, and is a possible mechanism for lunar surface ageing and compositional modification. The measurements were performed in order to assess the relative sputtering efficiency of protons, which are the dominant constituent of the solar wind, and less abundant heavier multicharged solar wind constituents, which have higher physical sputtering yields than same-velocity protons, and whose sputtering yields may be further enhanced due to potential sputtering. Two different target preparation approaches using JSC-1A AGGL lunar regolith simulant are described and compared using SEM and XPS surface analysis. (C) 2010 Published by Elsevier B.V.