Search

Abstract: Nanophase iron (np-Fe0) particles produced by space weathering have been widely observed in lunar soil. Current research suggests that np-Fe0 could have important effects on the chemical, optical and magnetic properties of the lunar soil. To investigate the relationship between np-Fe0 and these properties of lunar soil, simulation of the production process of np-Fe0 by space weathering is necessary because of the scarcity of lunar samples for research purposes. New methods using microwave heating and magnetron sputtering techniques to simulate np-Fe0 production both in the glass phase and on the grain surfaces, respectively, are investigated in this study. Both the formation and occurrence of np-Fe0 are taken into account in the experiment. The X-ray Diffraction (XRD) spectra show that metallic iron has formed in the glass phase produced by microwave heating of ilmenite. Using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), the size of np-Fe0 particles produced in a microwave heating experiment, which is held for 8min at 1300°C, is determined to be about 100–500nm. Compared to the glass of lunar sample 10084, the major composition of the glass matrix is formed by microwave heating compares favorably. In magnetron sputtering experiment the size of np-Fe0 particles is about 20–30nm, and appears on the grain surfaces. The characteristics of np-Fe0 produced in the simulations are consistent with those of lunar samples documented in the literature. [Copyright &y& Elsevier]

Abstract: Reliable measurements of the Moon''s global heat flow would serve as an important diagnostic test for models of lunar thermal evolution and would also help to constrain the Moon''s bulk abundance of radioactive elements and its differentiation history. The two existing measurements of lunar heat flow are unlikely to be representative of the global heat flow. For these reasons, obtaining additional heat flow measurements has been recognized as a high priority lunar science objective. In making such measurements, it is essential that the design and deployment of the heat flow probe and of the parent spacecraft do not inadvertently modify the near-surface thermal structure of the lunar regolith and thus perturb the measured heat flow. One type of spacecraft-related perturbation is the shadow cast by the spacecraft and by thermal blankets on some instruments. The thermal effects of these shadows propagate by conduction both downward and outward from the spacecraft into the lunar regolith. Shadows cast by the spacecraft superstructure move over the surface with time and only perturb the regolith temperature in the upper 0.8m. Permanent shadows, such as from thermal blankets covering a seismometer or other instruments, can modify the temperature to greater depth. Finite element simulations using measured values of the thermal diffusivity of lunar regolith show that the limiting factor for temperature perturbations is the need to measure the annual thermal wave for 2 or more years to measure the thermal diffusivity. The error induced by permanent spacecraft thermal shadows can be kept below 8% of the annual wave amplitude at 1m depth if the heat flow probe is deployed at least 2.5m away from any permanent spacecraft shadow. Deploying the heat flow probe 2m from permanent shadows permits measuring the annual thermal wave for only one year and should be considered the science floor for a heat flow experiment on the Moon. One way to meet this separation requirement would be to deploy the heat flow and seismology experiments on opposite sides of the spacecraft. This result should be incorporated in the design of future lunar geophysics spacecraft experiments. Differences in the thermal environments of the Moon and Mars result in less restrictive separation requirements for heat flow experiments on Mars. [Copyright &y& Elsevier]

Abstract: The development of a new process potentially useful for future manned Lunar and/or Martian space missions in the framework of the so-called ISRU (In-Situ Resource Utilization) and ISFR (In-Situ Fabrication and Repair) concepts is described and discussed in this work. This process involves the fabrication of physical assets by self-propagating high temperature synthesis (SHS) for construction applications in Lunar and Martian environments starting from different Lunar or Martian regolith simulants and aluminum, as reducing agent. In addition, although Moon and Mars already contain ilmenite (FeTiO3) and iron oxides, respectively, the latter ones are also added to the initial mixtures to promote suitable SHS reactions. A complete scheme for the fabrication of physical assets to be used as protection against solar rays, solar wind and meteoroids, where all required stages are indicated, is finally proposed in the framework of a recently filed patent. [Copyright &y& Elsevier]

The ARTEMIS mission takes two of the five THEMIS spacecraft beyond their prime mission objectives and reuses them to study the Moon and the lunar space environment. Although the spacecraft and fuel resources were tailored to space observations from Earth orbit, sufficient fuel margins, spacecraft capability, and operational flexibility were present that with a circuitous, ballistic, constrained-thrust trajectory, new scientific information could be gleaned from the instruments near the Moon and in lunar orbit. We discuss the challenges of ARTEMIS trajectory design and describe its current implementation to address both heliophysics and planetary science objectives. In particular, we explain the challenges imposed by the constraints of the orbiting hardware and describe the trajectory solutions found in prolonged ballistic flight paths that include multiple lunar approaches, lunar flybys, low-energy trajectory segments, lunar Lissajous orbits, and low-lunar-periapse orbits. We conclude with a discussion of the risks that we took to enable the development and implementation of ARTEMIS. [ABSTRACT FROM AUTHOR]

Abstract: The potential effect of the lunar exosphere on the near-ultraviolet sky background emission is predicted for Lunar-based Ultraviolet Telescope (LUT: a funded Chinese scientific payload for the Chang’e-III mission). Using the upper limit on the OH concentration inferred from the recent MIP CHACE results, our calculations show that the sky brightness due to the illuminated exosphere is <8.7photons−1 cm−2 arcsec−2 within the wavelength range 245–340nm. By evaluating the signal-to-noise ratios of observations of an AB=13mag point source at a series of sky background levels, our analysis indicates that the detection performance of LUT can be moderately degraded by the lunar exosphere emission in most cases. An AB=13mag point source can still be detected by the telescope at a signal-to-noise ratio more than 8 when the OH concentration is less than 2×108 moleculescm−3. However, the effect on the performance is considerable when the exosphere is as dense as suggested by CHACE. [Copyright &y& Elsevier]

Abstract: The non-condensing neutral helium exosphere is at its most concentrated levels on the cold lunar nightside. We show herein that these He atoms are susceptible to impact ionization from primary and secondary electrons flowing in the vicinity of the negatively-charged nightside lunar surface. The secondary electron beams are a relatively recent discovery and are found to be emitted from the nightside surface at energies consistent with the negative surface potential. The effect is to create an electron impact-created ionosphere in nightside regions, possibly especially potent within polar craters. [Copyright &y& Elsevier]

Abstract: Radio occultation measurements from the Soviet Luna 19 mission suggest that electron concentrations above the sunlit lunar surface can be significantly higher than that expected from either the photo-ionization of exospheric neutrals or any other well-known process. These measurements were used to infer the electron column concentrations above the lunar limb as a function of tangent height, which surprisingly indicated peak concentrations of ∼103 cm−3 at ∼5km altitude. It has been speculated that electrically charged exospheric dust could contribute to such electron populations. This possibility is examined here using the exospheric dust abundances inferred from Apollo 15 coronal photographs to estimate the concentration of electrons produced by photo- and secondary emission from dust. These estimates far exceed the electron concentrations predicted by any other suggested mechanism, and are within a factor of ≈20 of those inferred from the Luna 19 measurements. It is possible that this discrepancy is due to an under-estimate in dust grain capacitances and/or the presence of much higher exospheric dust abundances during the Luna 19 measurements. These results suggest that electrons emitted from exospheric dust could be responsible for the Luna 19 measurements, and that this process could dominate the formation and evolution of the lunar ionosphere. [Copyright &y& Elsevier]

By mid-19th century, astronomers strongly suspected that the Moon was largely dry and airless, based on the absence of any observable weather. [1] In 1892, William H. Pickering made a series of careful occultation measurements that allowed him to conclude that the lunar surface's atmospheric pressure was less than 1/4000th of Earth's. [2] Any number of strange ideas arose to contradict this, including Danish astronomer/mathematician Peter Andreas Hansen's hypothesis, that the Moon's center of mass is offset by its center of figure by 59 kilometers, meaning that one or two scale-heights of atmosphere could hide on the far side of the Moon, where it might support water oceans and life. [3] Hans Hörbiger's 1894 Welteislehre ("World Ice") theory, that the Moon and much of the cosmos is composed of water ice, became the favored cosmology of leaders of Third Reich Germany. [4] Respectable scientists realized that significant amounts of water on the Moon's surface would rapidly sublime into the vacuum. [ABSTRACT FROM AUTHOR]

Abstract: Lunar swirls are optically bright, sinuous albedo features found on the Moon. The Mini-RF synthetic aperture radar on the Lunar Reconnaissance Orbiter has provided a comprehensive set of X- and S-Band radar images of these enigmatic features, including the first radar observations of swirls on the farside of the Moon. A few general remarks can be made about the nature of the lunar swirls from this data set. First, the average radar properties of lunar swirls are identical to nearby non-swirl regions, in both total radar backscatter and circular polarization ratio (CPR). This implies that average centimeter-scale roughness and composition within the high-albedo portions of the swirls do not differ appreciably from the surroundings, and that the high optical reflectance of the swirls is related to a very thin surface phenomenon (less than several decimeters thick) not observable with X- or S-Band radar. Secondly, bright swirl material appears to be stratigraphically younger than a newly discovered impact melt flow at Gerasimovich D. This observation indicates that the swirls are capable of forming over timescales less than the age of the crater. The Mini-RF data set also provides clues to the origin of the lunar swirls. In at least one case, the presence of an enhanced crustal magnetic field appears to be responsible for the preservation of a high-albedo ejecta blanket around an otherwise degraded crater, Descartes C. The degree of degradation of Descartes C suggests it should not be optically bright, yet it is. This implies that the enhanced albedo is related to its location within a magnetic anomaly, and hence supports an origin hypothesis that invokes interaction between the solar wind and the magnetic anomaly. [Copyright &y& Elsevier]

Abstract: This paper analyzes a process that has been observed in simulations of numerous systems where ring material is strongly perturbed by a nearby moon. If the ring particles can be imparted with a forced eccentricity on the order of 10−5 in a single pass by the moon, particle orbits are observed to move towards regions of higher density as a result of the organized collisions that occur in the dense peaks of the satellite wake. The width of the ring can decrease by as much as 90% if the forced eccentricity is greater than 3×10−5 and the unperturbed geometric optical depth is greater than 0.03. The fractional change in ring width is relatively insensitive to the particle size so long as the particle radius is much less than the product of the semimajor axis and the forced eccentricity. Including a power law particle size distribution with slope of −2.8 spanning a decade in particle radius reduces the fractional width change by about 10% compared to the uniform particle-size case. Adding gravitational interactions between ring particles only has a significant effect on ring confinement if the unperturbed geometric optical depth exceeds .03, but a 40% reduction in ring width is still achieved in a self-gravitating ring of geometric optical depth 0.3 if the forced eccentricity exceeds 3×10−5. This process does not require the material to be in resonance with the moon, nor does it have any minimum mass constraints because particle self-gravity is not required. The collisional damping of satellite wakes therefore provides a simple mechanism by which a single moon can reduce the radial extent of any ringlet that is close to it and has sufficient optical depth for collisions to be significant. [Copyright &y& Elsevier]

Abstract: We present a general self-consistent kinetic theory for plasma sheath formation in solar wind plasma. The theory could be applied to anisotropic, as well as to isotropic collisionless plasma without resorting to any simplifications, limitations, or assumptions, such as the necessary existence of a ‘pre-sheath’ region of ions acceleration to ensure the Bohm criterion. The kinetic framework is first applied to sheath formation around an arbitrary oriented planar absorbing surface, charged by solar wind anisotropic plasma, under the condition of negligible photoelectric effect. We then make use of our kinetic approach for the plane geometry in isotropic collisionless plasma, as a particular case of a planar electrode orientation parallel to plasma streaming velocity, also analyzing the sheath structure around spherical and cylindrical absorbing electrodes submerged in isotropic collisionless plasma. Obtained results demonstrate principal differences in spatial charge distributions in sheath regions between spherical or cylindrical electrodes of large size and an unbound planar surface submerged in isotropic plasma. In the case of a planar electrode, we directly compare results obtained in our kinetic and hydrodynamic theories and conventional hydrodynamic theory of plasma sheath formation. The outcome from the present study have direct implications to the analysis of plasma sheath structure and associated distribution in space of charged dust grains, which is relevant to the moon exploration near the optical terminator region or in shadowed craters in the moon. [ABSTRACT FROM AUTHOR]

Abstract: The altitudinal/latitudinal profile of the lunar atmospheric composition on the sunlit side was unraveled for the first time by the Chandra’s Altitudinal Composition Explorer (CHACE) on the Moon Impact Probe, a standalone micro-satellite that impacted at the lunar south pole, as a part of the first Indian mission to Moon, Chandrayaan-1. Systematic measurements were carried out during the descent phase of the impactor with an altitude resolution of ∼250m and a latitudinal resolution of ∼0.1°. The overall pressure on the dayside and the neutral composition in the mass range 1–100amu have been measured by identifying 44 and 18amu as the dominant constituents. Significant amounts of heavier (>50amu) species also have been detected, the details of which are presented and discussed. [Copyright &y& Elsevier]

The Clouds and the Earth’s Radiant Energy System (CERES) scanning radiometers have been operating to make raster scans of the moon on a quarterly basis to validate the point response function for the three channels of flight models 1–4 aboard the Terra and Aqua spacecraft. Instrument pointing accuracy was verified by this method to 0.2° for the total channel of FM-3. The point response functions were computed from the lunar observations and were found to be nominal with the exception of the FM-2 window channel, which was found to have a region of high sensitivity. This anomaly is attributed to a delamination of the detector flake from the heat sink in that region. The influence of this anomaly is accounted for by the in-flight calibration and has no adverse effect on the application of the data. [ABSTRACT FROM AUTHOR]

Abstract: The cloud amount summer nighttime data obtained from the 1994 to 2007 NASA satellite infrared and visible range measurements taken within the framework of the International Satellite Cloud Climatology Project (ISCCP) were analyzed, and the contribution by lunar signal to the cloud amount was extracted. Although the fact of lunar influence on cloudiness is known, this investigation has made it possible to separate the lunar-phase and lunar-declination effects on cloudiness. The relative cloud amount tends to grow with a change in lunar phase from a quadrature to the New Moon or Full Moon and with an increase in lunar declination by absolute value. Both the effects are statistically significant, the lunar-declination effect is a little stronger. The obtained results do not seem to contradict the theory of lunar tides. [Copyright &y& Elsevier]

Abstract: The Cassini mission revealed two spectacular characteristics of Iapetus: (1) a geologically old and high equatorial ridge, which is unique in the Solar System and (2) a large flattening of 35km consistent with the equilibrium figure for a hydrostatic body rotating with a period of 16h, whereas the current spin period is 79.33 days. This study describes three-dimensional simulations of solid-state convection within an undifferentiated Iapetus. It investigates the implications for the evolution of the interior thermal structure and its spin rate and global shape using radially layered viscoelastic models. The role of the concentration in the short-lived radiogenic element [26Al], just after accretion is completed, is specifically addressed. The first result is to show that whatever the [26Al] value, convection occurs. As suggested by Castillo-Rogez et al. [Castillo-Rogez, J., Matson, D., Sotin, C., Johnson, T., Lunine, J., Thomas, P. [2007] Icarus, 190, 179–202], convection reduces the warming of the interior compared to the conductive evolution and therefore limits the conditions for despinning. In our calculations, two conceptual linear viscoelastic models are used. When considering a Maxwell rheology, the interior temperature (viscosity) never reaches a value high (low) enough to induce despinning. In order to promote dissipation at low temperature, a Burgers rheology, which includes an additional dissipation peak, is introduced. For favorable parameter values, this latter rheology leads to despinning. However, only models associated with large amounts of short-lived radiogenic elements lead to the observed flattening. This suggests that the accretion process needs to be completed shortly after the formation of CAIs (Calcium–Aluminum-rich Inclusions) (⩽4Myr). For [26Al] varying between 72 and 46ppb, the observed flattening is obtained only for a limited range of initial spin period, between 9.5 and 10.2h. For [26Al] ranging between 30 and 15ppb, initial spin rates smaller than 8.5h are required. For smaller values of [26Al], the body is too cold and viscous to acquire a significant flattening even if a rotation period close to the body disruption limit is considered. Even with a thin lithosphere during the early stage, our simulations show that Iapetus never reaches the equilibrium figure for a hydrostatic body due to the non-zero rigidity of the lithosphere. The 35km value of the flattening is the result of the partial relaxation of an ancient larger flattening ranging between 45 and 80km, depending on the evolution of the lithosphere thickness mainly controlled by the radiogenic content. A thin lithosphere is consistent with an early building of the equatorial ridge. The lithosphere thickening due to interior cooling can explain the preservation of the ridge throughout the remaining evolution of Iapetus. [Copyright &y& Elsevier]

Abstract: We produced regional geologic maps of the Hi’iaka and Shamshu regions of Io’s antijovian hemisphere using Galileo mission data to assess the geologic processes that are involved in the formation of Io’s mountains and volcanic centers. Observations reveal that these regions are characterized by several types of volcanic activity and features whose orientation and texture indicate tectonic activity. Among the volcanic features are multiple hotspots and volcanic vents detected by Galileo, one at each of the major paterae: Hi’iaka, Shamshu, and Tawhaki. We mapped four primary types of geologic units: flows, paterae floors, plains, and mountains. The flows and patera floors are similar, but are subdivided based upon emplacement environments and mechanisms. The floors of Hi’iaka and Shamshu Paterae have been partially resurfaced by dark lava flows, although portions of the paterae floors appear bright and unchanged during the Galileo mission; this suggests that the floors did not undergo complete resurfacing as flooding lava lakes. However, the paterae do contain compound lava flow fields and show the greatest activity near the paterae walls, a characteristic of Pele type lava lakes. Mountain materials are tilted crustal blocks that exhibit varied degrees of degradation. Lineated mountains have characteristic en echelon grooves that likely formed as a result of gravitational sliding. Undivided mountains are partially grooved but exhibit evidence of slumping and are generally lower elevation than the lineated units. Debris lobes and aprons are representative of mottled mountain materials. We have explored the possibility that north and south Hi’iaka Mons were originally one structure. We propose that strike-slip faulting and subsequent rifting separated the mountain units and created a depression which, by further extension during the rifting event, became Hi’iaka Patera. This type of rifting and depression formation is similar to the mechanism of formation of terrestrial pull-apart basins. With comparison to other regional maps of Io and global studies of paterae and mountains, this work provides insight into the general geologic evolution of Io. [Copyright &y& Elsevier]

Abstract: Impacts of comets and asteroids play an important role in volatile delivery on the Moon. We use a novel method for tracking vapor masses that reach escape velocity in hydrocode simulations of cometary impacts to explore the effects of volatile retention. We model impacts on the Moon to find the mass of vapor plume gravitationally trapped on the Moon as a function of impact velocity. We apply this result to the impactor velocity distribution and find that the total impactor mass retained on the Moon is approximately 6.5% of the impactor mass flux. Making reasonable assumptions about water content of comets and the comet size–frequency distribution, we derive a water flux for the Moon. After accounting for migration and stability of water ice at the poles, we estimate a total – metric tons of water is delivered to the Moon and remains stable at the poles over 1Ga. A factor of 30 uncertainty in the estimated cometary impact flux is primarily responsible for this large range of values. The calculated mass of water is sufficient to account for the neutron fluxes poleward of 75° observed by Lunar Prospector. A similar analysis for water delivery to the Moon via asteroid impacts shows that asteroids provide six times more water mass via impacts than comets. [Copyright &y& Elsevier]

Abstract: Direct detection of water in its vapour phase in the tenuous lunar environment through in situ measurements carried out by the Chandra’s Altitudinal Composition Explorer (CHACE) payload, onboard the Moon Impact Probe (MIP) of Chandrayaan I mission vindicates the presence of water on the surface of the moon in form of ice at higher lunar latitudes inferred from IR absorption spectroscopy, (especially that of OH), by the Moon Mineralogy Mapper (M3) of Chandrayaan I. The quadrupole mass spectrometer based payload, CHACE, sampled the lunar neutral atmosphere every 4s with a broad latitudinal (∼40°N to 90°S, with a resolution of ∼0.1°) and altitudinal (from 98km up to impact on the lunar surface with a resolution of ∼0.25km) coverage in the sunlit side of the moon for the first time. These two (CHACE and M3) complementary experiments are shown to collectively provide unambiguous signatures for the distribution of water in solid and gaseous phases in Earth’s moon. [Copyright &y& Elsevier]

Abstract: The Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft will orbit the Moon at an altitude of ≈50km with a payload that includes the Ultraviolet Spectrometer (UVS) instrument, which will obtain high spectral resolution measurements at near-ultraviolet and visible wavelengths (≈231–826nm). When LADEE/UVS observes the lunar limb from within the shadow of the Moon it is anticipated that it will detect a lunar horizon glow (LHG) due to sunlight scattered from submicron exospheric dust, as well as emission lines from exospheric gases (particularly sodium), in the presence of the bright coronal and zodiacal light (CZL) background. A modularized code has been developed at NMSU for simulations of scattered light sources as observed by orbiting instruments in lunar shadow. Predictions for the LADEE UVS and star tracker cameras indicate that LHG, sodium (Na) emission lines, and CZL can be distinguished based on spatial morphology and spectral characteristics, with LHG dominant at blue wavelengths (∼250–450nm) and small tangent heights. If present, LHG should be readily detected by LADEE/UVS and distinguishable from other sources of optical scattering. Observations from UVS and the other instruments aboard LADEE will significantly advance our understanding of how the Moon interacts with the surrounding space environment; these new insights will be applicable to the many other airless bodies in the solar system. [Copyright &y& Elsevier]

Abstract: In the absence of comprehensive seismic data coverage, the size, composition and physical state of the lunar core are still debated. It has been suggested that a dense ilmenite-rich layer, which originally crystallised near the top of the lunar magma ocean, may have sunk to the centre of the Moon to form either an outer core, surrounding a small metallic inner core, or a complete core if the lunar metallic iron content is insignificant. Here we study the formation, gravitational stability and thermal evolution of both an ilmenite-rich outer core and a full ilmenite-rich core, using a two-dimensional cylindrical thermo-chemical convection model. Gravity acceleration in the lunar mantle decreases quickly with depth. Since the gravity acceleration directly influences the buoyancy of materials, the low gravity acceleration near the centre was explicitly taken into account. Core formation and evolution were investigated by assessing the effects of varying two parameters, the Mg# (density) and the internal heat production of the ilmenite-rich layer. Varying these parameters changes the compositional and thermal buoyancy of the dense layer. Models show that a stable ilmenite-rich (outer) core may indeed have formed in the lunar interior and that its density depends on the internal heating in and the Mg# of the ilmenite-rich layer. Furthermore, the sharpness of the core-mantle boundary is shown to depend on the internal heat production in the ilmenite-rich material. Surprisingly, a higher internal heat production results in a sharper core-mantle boundary and a higher ilmenite content in the core. This is caused by lower viscosities as a result of higher temperatures. Although maximum core temperatures vary between different models by 700–1000K around 2Gyr after the start of the models, present-day estimates vary by only about 350–500K. Further narrowing of the range of internal heating values is essential for a better determination of both the present day lunar core temperature and its physical state. [Copyright &y& Elsevier]

The Baltic-Finnish and the Baltic (Latvian and Lithuanian) cosmonyms mostly coincide while the Baltic and Slavic cosmonymic patterns are different. The Pleiades in the Eastern Baltic are 'a sieve', the Milky Way is 'the path of migratory birds' and a girl holding water pails is seen on the Moon. Across most of Central, Western and Southern Europe the Pleiades are 'a hen with its chicken', the Milky Way and the lunar spots have other (and different) interpretations. The Eastern Baltic pattern is identical with the Middle Volga one where it is widespread among both Finnish-Permian and Turkic groups and probably relates back to the (Proto-Baltic?) culture of the Iron Age. However, parallels for the cosmonyms in question are found across most of Northern Eurasia and find corresponding similarities in some parts of North America. 'Water-carrier on the Moon' is the most widespread of these motifs being known in Japan and Polynesia. In Eurasia, the Northern Samoyeds noticeably lack all three images. The initial emergence of at least some of the cosmonyms under discussion in the Terminal Pleistocene of northern East Asia and their further dissemination towards the West, down to the Baltics, is a hypothesis to be checked. [ABSTRACT FROM AUTHOR]

Abstract: Observations of the equatorial lunar sodium emission are examined to quantify the effect of precipitating ions on source rates for the Moon’s exospheric volatile species. Using a model of exospheric sodium transport under lunar gravity forces, the measured emission intensity is normalized to a constant lunar phase angle to minimize the effect of different viewing geometries. Daily averages of the solar Lyman α flux and ion flux are used as the input variables for photon-stimulated desorption (PSD) and ion sputtering, respectively, while impact vaporization due to the micrometeoritic influx is assumed constant. Additionally, a proxy term proportional to both the Lyman α and to the ion flux is introduced to assess the importance of ion-enhanced diffusion and/or chemical sputtering. The combination of particle transport and constrained regression models demonstrates that, assuming sputtering yields that are typical of protons incident on lunar soils, the primary effect of ion impact on the surface of the Moon is not direct sputtering but rather an enhancement of the PSD efficiency. It is inferred that the ion-induced effects must double the PSD efficiency for flux typical of the solar wind at 1AU. The enhancement in relative efficiency of PSD due to the bombardment of the lunar surface by the plasma sheet ions during passages through the Earth’s magnetotail is shown to be approximately two times higher than when it is due to solar wind ions. This leads to the conclusion that the priming of the surface is more efficiently carried out by the energetic plasma sheet ions. [Copyright &y& Elsevier]

Abstract: The column densities of impact-produced metal atoms in the exosphere during the peaks of activity of the main meteor showers – Geminids, Quadrantids and Perseids – and during quiet periods are estimated. The Na supply rate is estimated to be 2×104, 3×103, 104, and 2×104 atomscm−2 s−1 for sporadic meteoroids, Perseid, Geminid, and Quadrantid meteor showers, respectively. A low upper limit on Ca in the lunar exosphere is explained by the condensation of Ca into dust grains during expansion of the cooling impact-produced vapor cloud. The chemical composition of gas-phase species released to the lunar exosphere during meteoroid impacts has been estimated. Most impact-produced molecules that contain metals are destroyed by solar photons while on ballistic trajectories. Energies of Na, K, Ca, and Mg atoms produced via photolysis of the respective monoxides are estimated to be 0.4, 0.35, 0.6, and 0.45eV, respectively. The relative content of impact-produced Na and K atoms is maximal at altitudes of about 1000–2000km and during the main meteor showers, lunar eclipses, and passages of the Moon through the Earth’s magnetosphere. [Copyright &y& Elsevier]

A robotic observatory has been setup in the south-west of Spain with the aim to study meteoroids interacting with the Earth's atmosphere and meteoroids impacting on the Moon's surface. This is achieved by using an array of high-sensitivity CCD video cameras and three automated Schmidt-Cassegrain telescopes. We summarize here the main characteristics of this new facility. [ABSTRACT FROM AUTHOR]

This study compares the latest Unified Lunar Control Network, ULCN 2005, solution with the earlier ULCN 1994 solution at global and local scales. At the global scale, the relative rotation, translation, and deformation (normal strains and shears) parameters between the two networks are estimated as a whole using their colocated station Cartesian coordinate differences. At the local scale, the network station coordinate differences are examined in local topocentric coordinate systems whose origins are located at the geometric center of quadrangles and tetrahedrons. This study identified that the omission of the topography in the old ULCN solutions shifted the geometric center of the lunar figure up to 5 km in the lunar equatorial plane and induced a few hundred-meter level global rotations of the ULCN 1994 reference frame with respect to ULCN 2005. The displacements between the old and new control networks are less than ±± 2 km on the average at the local scale, which behave like translations, caused by the omission of lunar topography in the earlier solution. The contribution of local rigid body rotations and dilatational and compressional components to the local displacements are approximately ±± 100 m for a quadrangle/tetrahedron of an average side length of 10 km. [ABSTRACT FROM AUTHOR]

The parameters of various lunar figures are of interest to the scientific community working on lunar exploration. In this study, the size of the geometrically best fitting triaxial and rotational ellipsoids, and spheres, are estimated using the method of condition equations with common unknown parameters from the coordinates of 271,610 control points of the newly available lunar control, ULCN 2005. In the first set of solutions, the origin of the figures is calculated with respect to the center of the mass of the Moon. Their origins are set to coincide with the lunar center of mass in the second set of solutions. The new estimates are the most up-to-date values for the triaxial and rotational ellipsoidal and spherical parameters of the lunar figures and are significantly different up to half a km as compared to the most recent solutions. [ABSTRACT FROM AUTHOR]

Abstract: The gravitational anomalies of the Moon have never been completely mapped; in particular, those on the hidden side are known only through the interpolation of data obtained for the visible side. Many space agencies around the world are developing new plans for the exploration of the Moon, hence a more precise knowledge of lunar harmonics could be useful for the planning of future missions. The aim of this study is to demonstrate the feasibility of a micro-satellite mission for the accurate mapping of high order lunar harmonics, generated by density anomalies, on the hidden side of the Moon. The mission, conceived within the School of Aerospace Engineering, at the University of Rome “La Sapienza”, employs two small probes (whose masses will be under 100kg), placed in two orbits around the Moon, with a fixed ratio between their orbital periods. The main probe will essentially be a relay satellite placed in a higher and eccentric orbit, always facing the Earth; a smaller probe will be in a low circular, near-polar, orbit. A reference signal would be sent from a net of Earth stations, and relayed by the relay satellite to the smaller probe, that reflects the signal back to the relay satellite, and then to Earth. A subsequent analysis of the Doppler effect on the downlink signal, with respect to the uplink, will allow to build a map of Moon gravitational field. The interesting aspect of this method of measurement is that there is no need to carry any kind of instrumentation for Doppler effect detection, including a stable frequency reference, on board. This allows the reduction of overall costs and technical complexity of the mission. The encouraging results of this study show the possibility of the realization of the mission in the short term, and with a limited budget, given the collaboration between universities, the aerospace industry, and any space agency. [Copyright &y& Elsevier]

Abstract: We developed a seismometer system for a hard landing “penetrator” probe in the course of the former Japanese LUNAR-A project to deploy new seismic stations on the Moon. The penetrator seismometer system (PSS) consists of two short-period sensor components, a two-axis gimbal mechanism for orientation, and measurement electronics. To carry out seismic observations on the Moon using the penetrator, the seismometer system has to function properly in a lunar environment after a hard landing (impact acceleration of about 8000G), and requires a signal-to-noise ratio to detect lunar seismic events. We evaluated whether the PSS could satisfactorily observe seismic events on the Moon by investigating the frequency response, noise level, and response to ground motion of our instrument in a simulated lunar environment after a simulated impact test. Our results indicate that the newly developed seismometer system can function properly after impact and is sensitive enough to detect seismic events on the Moon. Using this PSS, new seismic data from the Moon can be obtained during future lunar missions. [Copyright &y& Elsevier]

The results of numerical simulation of the general circulation in the Titan’s atmosphere at heights from 0 to 250 km are presented, obtained using a new model based on numerical solution of complete equations of motion of viscous compressible gas at the temperature distribution given by an empirical model. The model uses no hydrostatic equation and, as compared with traditional models, has higher resolution in vertical and over horizon. The results presented differ from results of other models and agree with the vertical profile of the zonal component of wind velocity measured by the Huygens spacecraft. Interpretation of this profile is given, including its main peculiarity consisting in a nonmonotonic behavior at heights from 60 to 75 km. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we re-examined the fundamental physics of charging of a dust particle in the moon environment by tenuous anisotropic solar wind plasma. The majority of work on dusty (complex) plasmas is largely concerns with laboratory plasmas, in which charging process of dust grains is very fast, thus making practical the working concept of dynamically equilibrium floating potential and grain charge. However, solar wind plasma parameters are considerably different at the moon orbit, and we found the characteristic charging time of lunar dust grains to be considerably longer, ranging from 3 to 4.6min for micron size particles, and up to 7.6h for 10-nm grains, depending on the value of plasma streaming velocity. These findings make it clear that the transient stage of charging process is important in the moon environment, and equilibrium floating potential and grain charge could be considered as long time asymptotic values. For this reason we re-formulated the moon dust charging process as an inherently time-dependent problem and derived the time-dependent charging equation for the grain potential for general case of anisotropic solar wind plasma. Using the results of our kinetics analysis we found that the distribution of charge density over grain surface submerged into solar wind plasma is highly anisotropic, thus making the OML model, which is based on the assumption of isotropic distribution of surface charge density, not applicable to the grain charging problem by the solar wind plasma. [Copyright &y& Elsevier]

The Moon is generally thought to have formed from the debris ejected by the impact of a planet-sized object with the proto-Earth towards the end of planetary accretion. Models of the impact process predict that the lunar material was disaggregated into a circumplanetary disk and that lunar accretion subsequently placed the Moon in a near-equatorial orbit. Forward integration of the lunar orbit from this initial state predicts a modern inclination at least an order of magnitude smaller than the lunar value-a long-standing discrepancy known as the lunar inclination problem. Here we show that the modern lunar orbit provides a sensitive record of gravitational interactions with Earth-crossing planetesimals that were not yet accreted at the time of the Moon-forming event. The currently observed lunar orbit can naturally be reproduced via interaction with a small quantity of mass (corresponding to 0.0075-0.015 Earth masses eventually accreted to the Earth) carried by a few bodies, consistent with the constraints and models of late accretion. Although the encounter process has a stochastic element, the observed value of the lunar inclination is among the most likely outcomes for a wide range of parameters. The excitation of the lunar orbit is most readily reproduced via collisionless encounters of planetesimals with the Earth-Moon system with strong dissipation of tidal energy on the early Earth. This mechanism obviates the need for previously proposed (but idealized) excitation mechanisms, places the Moon-forming event in the context of the formation of Earth, and constrains the pristineness of the dynamical state of the Earth-Moon system. [ABSTRACT FROM AUTHOR]

An overview of a minor topographical lunar feature situated in the foothills of the ‘Altai Scarp’, with reference to its brief appearance in a little known astronomical publication, from which sketch drawings are compared with recent visual observations. [ABSTRACT FROM AUTHOR]

Abstract: We have extended our Monte Carlo model of exospheres [Wurz, P., Lammer, H., 2003. Icarus 164 (1), 1–13] by treating the ion-induced sputtering process from a known surface in a self-consistent way. The comparison of the calculated exospheric densities with experimental data, which are mostly upper limits, shows that all of our calculated densities are within the measurement limits. The total calculated exospheric density at the lunar surface of about as result of solar wind sputtering we find is much less than the experimental total exospheric density of about . We conclude that sputtering contributes only a small fraction of the total exosphere, at least close to the surface. Because of the considerably larger scale height of atoms released via sputtering into the exosphere, sputtered atoms start to dominate the exosphere at altitudes exceeding a few 1000 km, with the exception of some light and abundant species released thermally, e.g. H2, He, CH4, and OH. Furthermore, for more refractory species such as calcium, our model indicates that sputtering may well be the dominant mechanism responsible for the lunar atmospheric inventory, but observational data does not yet allow firm conclusions to be drawn. [Copyright &y& Elsevier]

The Moderate Resolution Imaging Spectroradiometer (MODIS) Protoflight Model on-board the Terra spacecraft and the MODIS Flight Model 1 on-board the Aqua spacecraft were launched on December 18, 1999 and May 4, 2002, respectively. They view the moon through the space view (SV) port approximately once a month to monitor the long-term radiometric stability of their reflective solar bands (RSB5). The lunar irradiance observed by MODIS depends on the viewing geometry. Algorithms were developed to select lunar views such that these geometric effects are minimized. In each MODIS lunar observation, the moon can be viewed in multiple scans. The lunar irradiance of a MODIS RSB can be derived from the response of all detectors of a spectral band in one scan which fully covers the moon, from that of one detector in multiple scans or from the response of all detectors in multiple scans. Based on lunar observations, a set of coefficients is defined and derived to trend MODIS system response degradation at the angle of incidence (AOl) of its SV port. It is shown that the degradation is both wavelength and mirror side dependent. Since launch, Terra and Aqua MODIS band 8 (412 nm) mirror side one have degraded 36% and 17%, respectively, at the AOl of the SV. A comparison between the lunar coefficients and those derived from the MODIS on-board solar diffuser (SD) calibrations shows that the response change of the MODIS RSB is both AOl and time dependent. Time-dependent response versus scan angle (RVS) lookup tables derived from lunar views, SD calibration, and Earth-view observations have been used to maintain the quality of the L1B data for both the Terra and Aqua MODIS RSB. The corrections provided by the RVS in the Terra and Aqua MODIS data from the 412-nm band are as large as 14% and 6.2%, respectively. [ABSTRACT FROM AUTHOR]

The Clementine UVVIS images and the spectral and chemical (mineral) characteristics of lunar soil samples previously measured by the Lunar Samples Characterization Consortium were used to map the plagioclase and clinopyroxene abundance in the lunar surface material. An excess of plagioclase was found in young highland craters (e.g., in the crater Tycho) and in their ray systems. For clinopyroxenes, analogous behavior was observed in mare craters (e.g., in the crater Aristarchus). The maps for the FeO and Al2O3 bulk contents and the contents of these oxides in plagioclase and clinopyroxene were estimated by the same technique. These maps were compared to each other and to the predicted distribution of the lunar regolith maturity. The regolith of highland ray systems (e.g., the Tycho crater system) is characterized not only by low maturity but also by peculiar iron and aluminum contents: the lower the soil maturity degree, the smaller the iron content and the greater the aluminum content. This is confirmed by the data for the lunar soil samples from the Apollo 16 landing site. A cluster analysis of the “clinopyroxene content-maturity” and “plagioclase content-maturity” correlation diagrams allowed the mineral mapping of the lunar surface to be performed. [ABSTRACT FROM AUTHOR]

Abstract: The part of a planet''s gravity that is coherent with its topography provides information about the deflection of its crust after loading, and hence the resistance of its lithosphere to bending at the time the load was emplaced. We used observed line of sight accelerations from Lunar Prospector, together with the accelerations we would have expected if anomalies in the gravity field were only caused by topography, to estimate the admittance and coherence between topography and gravity over several regions of the lunar nearside. We then compared our estimates to what we would expect if the lithosphere behaved as a floating elastic plate or shell, assuming a linear relationship between topography and gravity. We found in the region surrounding the southern highland crater Clavius that the data can be modeled using a thin plate with and uncorrelated loads at the surface and base of the upper crust. A spherical shell model with surface loading is less satisfactory: to fit the admittance adequately requires topography with wavelengths over 400 km to be formed when 1 km and the remainder when . By contrast, the apparent lack of compensation around the youngest giant impact basins requires a plate with or a shell with . Our results indicate the thickness of the lunar lithosphere increased from in the pre-Nectarian to in the Nectarian. [Copyright &y& Elsevier]

We analyze two lunar occultation lightcurves of the carbon star IRC +10216 (CW Leo). The two events were recorded in 1989 and 1998, in the near-infrared H and K bands respectively. The results consist of two extended (&ap;2″), high-resolution (&ap;0″.001), one-dimensional brightness profiles along position angles 164° and 304° at the two epochs. The profiles show evidence for a bright central spike of emission having a FWHM of 0″.035, which is consistent with what is predicted by current models for the photosphere of the central star in IRC +10216. This feature can be identified with the so-called A component recently revealed by speckle imaging [A&A 334 (1998) L5; A&A 357 (2000) 169; A&A 333 (1998) L51], and the so-called core of the southern component observed with the aperture masking technique by Tuthill et al. [ApJ 543 (2000) 284]. The B component, alternatively suggested to mark the actual location of the central star by Osterbart et al. [A&A 357 (2000) 169], also seems to show a FWHM consistent with the above value, but it is well detected only in the 1998 K-band lightcurve, while for the 1989 H-band data the detection is less evident. Our brightness profiles also reveal a wealth of other structures, on several levels of scale, which are consistent with models of episodic dust ejection from the central star [A&A 302 (1995) 483]. [Copyright &y& Elsevier]

The two isotopes of nitrogen, 14N and 15N. have relative abundances extremely variable among solar system reservoirs such as planets arid their atmospheres, primitive and differentiated meteorites. and comets. Expressed in the delta notation (δ15N = [[15N/14N]sample/[15N/14N]standard-1] × 1000, in parts per mil, or ‰ where the standard is atmospheric N having 15N/14N = 0.003676), δ15N ranges from -250‰ (the lower limit of lunar soil values) up to 1600‰ (measured in the meteorites benccubinites). The lunar surface constitutes a unique archive of the past corpuscular (solar and meteoritic) contributions to planetary surfaces. Nitrogen trapped in the lunar regolith presents a highly variable isotopic composition, which represents either secular variation of the solar wind composition although this possibility conflicts with the apparent isotope stability over time of other solar wind volatile elements, or more likely different contributions from solar corpuscular radiation and non-solar sources. In this ease. the solar nitrogen component is depleted by more than 24% in 15N. whereas non-solar, planetary sources (meteorites, micrometeorites, possibly comets) are enriched fri the heavy isotope of nitrogen by ≥10% on average. Variations in the nitrogen isotopic composition of lunar soils are explained by a secular change in the strength of the planetary flux. and a correlation between N isotopic compositions and surface exposure age tor different soils suggest that the planetary contribution to the inner solar system might have increased fri the last 0.4 Gy. The variability of the N isotope composition among solar system objects might be due to incomplete equilibration of nitrogen isotopes from different host phases of pre-solar origin. Alternatively, it could result from mixing between 15N-depleted protosolar nitrogen originally present in the gas and presolar solid (organic?) compounds enriched in 15N. [ABSTRACT FROM AUTHOR]

We discuss some of the major noble gas components on the Moon and their implications on the history of Moon and Sun. He, Ar, and Rn have been detected in the tenuous lunar atmosphere. The Ar and Rn abundances suggest that a sizeable fraction of the lunar interior presently loses all its freshly produced radiogenic noble gases. Part of the radiogenic Ar and Xe (the latter from 110W extinct radioactive isotopes of I and Pu) outgassed from the lunar interior later became retrapped in the dust grains on the lunar surface. These "parentless" gases may also he used to constrain the degassing history of the Moon. although a quantitative understanding Is lacking. The dust layer on the lunar surface contains large amounts of noble gases implanted by the solar wind. The lunar regolith therefore constitutes the best available archive of the solar history of the past four billion years. [ABSTRACT FROM AUTHOR]

The comet hypothesis of the origin of lunar ice, which was recently discovered in the polar regions of the moon by Lunar Prospector, is examined. It is shown that a comet impact produces a temporary atmosphere whose volatile component accumulates essentially completely in cold traps - the permanently shadowed regions of the Moon. The condensation of volatile compounds leads to the formation of ice with a definite chemical and isotopic composition, which contains important information about the composition of the comet. This hypothesis can be checked during the next lunar missions, and if confirmed, detinite progress will have been made in understanding the nature of comets. [Copyright &y& Elsevier]

We investigate the deposition of hydrogen at the lunar poles from the incident solar wind proton flux. We follow an incident solar wind proton as it interacts with the lunar surface, is emitted into the atmosphere, and migrate through a series of ballistic hops across the surface of the Moon. We trace the path of the particle until it is removed from the system by photo-processes such as ionization or dissociation, by thermal escape, by surface chemistry, or by reaching a cold trap. Iterating with various compounds formed through surface chemistry, we follow all hydrogen atoms input into the system, regardless of their molecular composition. Accumulating statistics on the outcomes for various input particles, we determine that .6 of the hydrogen forms H2 through chemical sputtering. Most of the remaining H thermally desorbs as atomic in a fraction of .27. Although the amount converted to OH is small (10%), most hydrogen reaches the pole through OH migration, .008 OH/H+. Finally, we calculate the amount of time required for the solar wind to supply the amount of hydrogen detected at the poles by the Lunar Prospector Neutron Spectrometer to be 7 Myr. If the poles only retain water due to the low freezing points of the other molecules, the time required is 100 Myr. [Copyright &y& Elsevier]

The seasonal variations of the lunar geomagnetic tide are analysed at a group of stations around the longitude of India. The position of the focus of the lunar ionospheric current system is found to move with season and to disappear in northern winter. A year-to-year variability of the phases is also demonstrated. The phase relationships indicate the presence of antisymmetric atmospheric tidal modes of various strengths in different seasons. The different lunar Hough mode amplitudes, derived earlier, may also explain the observed September maximum in the lunar horizontal magnetic component at the equator. [Copyright &y& Elsevier]