A latitudinal and radial study of the lunar sodium exosphere has been performed utilizing observations made from two different methods: (1) observations made at targeted altitudes using a Fabry-Perot Spectrometer (FPS) and (2) observations made from a coronagraph. The FPS observations made from the National Solar Observatory McMath-Pierce Solar Telescope, Kitt Peak, Arizona and the coronagraph observations were made at the Winer Observatory, Sonoita, Arizona. A small subset of the high resolution FPS observations were made concurrently with coronagraph measurements. Measured linewidths and linewidth-derived temperatures from FPS observa-tions were compared to temperatures derived from the coronagraphic intensity altitude profiles, with FPS linewidth-derived temperatures shown to be consistently lower. We suggest that the coronagraph method samples a velocity distribution perpendicular to the FPS's LOS, while the FPS samples a velocity distribution tangential to the lunar limb (i.e., along the FPS LOS). We also suggest that the coronagraph measurements may be more sensitive to the escaping population of atoms as the population close to the surface is not observed. The concurrent FPS measurements sit below the occulting disk of the coronagraph and measure the atoms closer to the surface. Furthermore, both the FPS linewidth-derived temperatures and the coronagraph scale heights show an increase towards high latitudes, an effect which is attributed to particle transport and/or contributions from a source like meteoroid impact vaporization. FPS linewidths decrease as a function of altitude, a result confirmed through a simulation of velocity distributions from nonthermal source mechanisms. And, finally, Linewidths are largest when looking over the dawn/dusk terminator. These results will enable improved characterization of the sources for the lunar sodium exosphere.

The PLanetary extreme Ultraviolet Spectrometer (PLUS) is a project funded by the Italian Space Agency focused on the development of an extreme (EUV) and far-ultraviolet (FUV) high-performance spectrograph, which adopts a dual channel optical scheme. Thanks to an optimized layout based on the use of Variable Line Space (VLS) gratings in an off-Rowland configuration, high spectral and spatial resolution are achieved. The efficiency improvement is obtained by the optimization of the coatings on the optical components. Improved detection limit, shorter observations integration time and unprecedented performance in terms of dynamic range will be achieved by the use of high resolution/dynamic range solar blind photon counting detectors. The photon counting detectors will be based on a Micro-Channel Plate (MCP) coupled with an Application Specific Integrated Circuit (ASIC) read out system.

Water ice, abundant in the outer solar system, is volatile in the inner solar system. On the largest airless bodies of the inner solar system (Mercury, the Moon, Ceres), water can be an exospheric species but also occurs in its condensed form. Mercury hosts water ice deposits in permanently shadowed regions near its poles that act as cold traps. Water ice is also present on the Moon, where these polar deposits are of great interest in the context of future lunar exploration. The lunar surface releases either OH or H2O during meteoroid showers, and both of these species are generated by reaction of implanted solar wind protons with metal oxides in the regolith. A consequence of the ongoing interaction between the solar wind and the surface is a surficial hydroxyl population that has been observed on the Moon. Dwarf planet Ceres has enough gravity to have a gravitationally-bound water exosphere, and also has permanently shadowed regions near its poles, with bright ice deposits found in the most long-lived of its cold traps. Tantalizing evidence for cold trapped water ice and exospheres of molecular water has emerged, but even basic questions remain open. The relative and absolute magnitudes of sources of water on Mercury and the Moon remain largely unknown. Exospheres can transport water to cold traps, but the efficiency of this process remains uncertain. Here, the status of observations, theory, and laboratory measurements is reviewed.

Global exosphere models of alkali gases surrounding Mercury and the Moon assume that the primary effect of the porous soil is to reduce the effective desorption rates. We demonstrate with a kinetic simulation that, following adsorption, the complicated structure of soils has two additional effects on the fate of previously released alkali atoms: (1) trapping of free atoms at lunar temperatures by microscopic shadows and inward diffusion, which becomes the primary sink mechanism, and (2) high-energy barriers for thermal desorption compared to what would be retrieved from experiments on thin films or compacted pellets, especially when surface diffusion of adsorbates is considered. Lunar soils retain one fifth to two thirds of recycled adsorbates, depending on the assumed adsorbate mobility, photodesorption cross section, and soil thermal gradient. A transition from a retentive surface to full outgassing atT > 500 K will produce complex feedback mechanisms of alkali circulation at Mercury.

The study of exospheres can help us understand the long-term loss of volatiles from planetary bodies due to interactions of planets, satellites, and small bodies with the interplanetary medium, solar radiation, and internal forces including diffusion and outgassing. Recent evidence for water and OH on the Moon has spurred interest in processes involving chemistry and sequestration of volatile species at the poles and in voids. In recent years, NASA has sent spacecraft to asteroids including Vesta and Ceres, and ESA sent Rosetta to comet 67P/Churyumov-Gerasimenko and the asteroids Lutetia and Steins. Japan's Hayabusa spacecraft returned a sample from asteroid Itakowa, and OSIRIS-REX will return a sample from a primitive asteroid, Bennu, to Earth. In a surface-bounded exosphere, the gases are derived from the surface and thus reflect the composition of the body's regolith, although not in a one-to-one ratio. Observation of an escaping exosphere, termed a corona, is challenging. We have therefore embarked on a parametrical study of exospheres as a function of mass of the exospheric species, mass of the primary body and source velocity distribution, specifically thermal (Maxwell-Boltzmann) and sputtering. The goal is to provide a quick look to determine under what conditions and for what mass of the primary body the species of interest are expected to be bound or escaping and to quickly estimate the observability of exospheric species. This work does not provide a comprehensive model but rather serves as a starting point for further study. These parameters will be useful for mission planning as well as for students beginning a study of planetary exospheres. Published by Elsevier Ltd on behalf of COSPAR.

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.

The paper discusses the formation and dynamics of the rarefied gas envelope near the icy surface of Jupiter's moon Ganymede. Being the most massive icy moon, Ganymede can form a rarefied exosphere with a relatively dense near-surface layer. The main parent component of the gas shell is water vapor, which enters the atmosphere due to thermal degassing, nonthermal radiolysis, and other active processes and phenomena on the moon's icy surface. A numerical kinetic simulation is performed to investigate, at the molecular level, the formation, chemical evolution, and dynamics of the mainly H2O- and O-2-dominant rarefied gas envelopes. The ionization processes in these rarefied gas envelopes are due to exposure to ultraviolet radiation from the Sun and the magnetospheric plasma. The chemical diversity of the icy moon's gas envelope is attributed to the primary action of ultraviolet solar photons and plasma electrons on the rarefied gas in the H2O- or O-2-dominant atmosphere. The model is used to calculate the formation and development of the chemical diversity in the relatively dense near-surface envelope of Ganymede, where an important contribution comes from collisions between parent molecules and the products of their photolysis and radiolysis.

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.

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.

A 10-cm aperture telescope equipped with coronagraphic capabilities, using occulting masks of various size and material, has been developed to obtain low-light-level, wide-angle (similar to 7(o) FOV), narrow-band filtered images of sodium exospheres at Io, the Moon and Mercury. Here we describe new instrument capabilities and recent findings about the extraordinarily long tails of sodium gas discovered in the lunar and hermean exospheres. Spatial and temporal variability patterns captured in such images can be used to study changes in surface sputtering processes and radiation pressure acceleration effects in the inner solar system.