Lunar Highlands Research Articles

Thermal Optical Properties of Lunar Dust Simulants

The total reflectance spectra of lunar simulant dusts (<20 m particles) were measured to determine their integrated solar absorptance and their thermal emittance for the purpose of analyzing the effect of dust on the performance of thermal control surfaces. All of the simulants exceptMinnesota Lunar Simulant 1 had awavelengthdependant reflectivity near 0.10 over the wavelength range of 8–25 m, and so are highly emitting at room temperature and lower. The anomalous behavior ofMinnesota Lunar Simulant 1 was attributed to its very low glass content. The 300 K emittance of all the lunar simulants, except Minnesota Lunar Simulant 1, ranged from 0.78 to 0.92. In all cases, the was lower for the <20 m particles than for larger particles reported earlier. There was considerably more variation in the lunar simulant reflectance in the solar spectral range (250–2500 nm) than in the thermal infrared. As expected, the lunar highlands simulants were more reflective in this wavelength range than the lunar mare simulants. The maxima at the Christiansen frequency were consistent with simulants being largely plagioclase and confirmed that, with the exception ofMinnesota Lunar Simulant 1P, addition of agglutinates did not change the mineralogical character of the simulants. The of the simulants ranged from 0.39 to 0.75. This is lower than values reported earlier for larger particles of the same simulants (0.41–0.82) and for representative mare and highlands lunar soils (0.74–0.91). Because the of somemare simulantsmore closelymatched that of highlands lunar soils, it is recommended that and values be the criteria for choosing a simulant for assessing the effects of dust on thermal control surfaces, rather than whether a simulant has been formulated as a highlands or a mare simulant.

Impact ionization mass spectra of anorthite cosmic dust analogue particles

Anorthite, the Ca‐rich end‐member of plagioclase feldspar, is a dominant mineral component of the Lunar highlands. Plagioclase feldspar is also found in comets, meteorites and stony asteroids. It is therefore expected to contribute to the population of interplanetary (and circumplanetary) dust grains within the solar system. After coating micron‐ and submicron‐sized grains of Anorthite with a conductive layer of Platinum, the mineral was successfully accelerated to hypervelocity speeds in the Max Planck Institut für Kernphysik's Van de Graaff accelerator. We present impact ionization mass spectra generated following the impacts of anorthite grains with a prototype mass spectrometer (the Large Area Mass Analyser, LAMA) designed for use in space, and discuss the behavior of the spectra with increasing impact energy. Correlation analysis is used to identify the compositions and sources of cations present in the spectra, enabling the identification of several molecular cations (e.g., CaAlO2, CaSiO2, Ca2AlO3/CaAlSi2O2) which identify anorthite as the progenitor bulk grain material.

月隕石（MIL 090034， 090036， 090070）の全岩化学組成に基づく月地殻の形成過程

月隕石（MIL 090034， 090036， 090070）の全岩化学組成に基づく月地殻の形成過程

Comparative study of the surface roughness of the Moon, Mars and Mercury

We analyze and compare the surface roughness of the Moon, Mercury and Mars by characterizing the scale-dependence of the slope distribution. We calculate the absolute and differential slopes at baselines ranging between a few hundreds of meters and hundred kilometers depending on the spatial resolutions of the datasets. For each planetary body, we analyze two types of terrains: the rough and old heavily cratered “highlands” regions and smoother and younger “plains” terrains, Mare on the Moon, northern plains on Mercury and Mars. The resulting curves are discussed in terms of the geological processes that shape the surfaces of terrestrial planets. We concentrate in particular on the Median Differential Slope (MDS), a measure of roughness that has already proven its relevance for the analysis of Martian and Lunar topography. The comparison of the MDS vs. baseline curves for different types of terrains on each planet reveals interesting common trends as well as intriguing differences. The Lunar highlands display the highest values of MDS at baselines larger than 2km but Mercury highlands seem to be slightly rougher at shorter baselines. Mars southern plateaus appear much smoother at all scales. On each planet, younger terrains show lower roughness than old terrains at long baselines. However, because they display a strong negative slope of MDS vs. baseline, the contrast of roughness between young and old terrains is fainter at short baseline.

Major elements and Mg# of the Moon: Results from Chang’E-1 Interference Imaging Spectrometer (IIM) data

Major elements such as Fe, Ti, Mg, Al, Ca, and Si play very important roles in understanding the origin and evolution of the Moon. Up to now there are still no high resolution maps for all the six major elements and Mg# showing their abundances and distributions. The objective of this paper is to introduce the techniques and results to create high resolution maps of the six major elements with Chang’E-1 Interference Imaging Spectrometer (IIM) data. The elemental contents of returned soils and feldspathic lunar meteorites are used as ground truth and correlated with the reflectance of the landing sites and northern farside highlands extracted from Chang’E-1 IIM data. The relationships linking geochemical information and optical data are established with empirical methods. The final maps of the abundances of the six major oxides are produced with the modified partial least squares regression (PLSR) model at a spatial resolution of 200m/pixel at the equator. Finally some implications (for example, producing the high resolution map of Mg#; identifying the crustal heterogeneity of lunar highlands; helping to search for HA basalts; assessing the average elemental abundances of each terrane and the whole Moon) of these new maps are shown.

Study of scattering characteristics of lunar equatorial region using Chandrayaan-1 Mini-SAR polarimetric data

The miniaturized synthetic aperture radar Mini-SAR onboard Indian Chandrayaan-1 mission was the first ever lunar orbiting SAR that acquired several data strips covering a wide variety of geological units over lunar equatorial and low latitude regions, some of which were not studied earlier at radar wavelengths. The Mini-SAR observations, complemented by high resolution optical imagery and higher incidence angle radar datasets, were effectively used to create a catalog of SAR backscatter properties of various lunar geological features. The radar backscatter along with the parameters circular polarization ratio (CPR), relative phase (δ) and m (the degree of polarization)–chi (the Poincare ellipticity) decomposition technique were used to study the scattering mechanisms, surface/sub-surface roughness and regional topography of some of the craters and their ejecta fields. The study revealed that the Taylor and Descartes craters in the lunar highlands region were characterized by high backscatter and low CPR values, while the Maunder and Kopff craters in the Mare Orientale basin were characterized by relatively low backscatter and elevated CPR values. The fresh crater Jackson and its ejecta blankets on the lunar far-side showed very high backscatter along with elevated CPR values due to the presence of abundant wavelength-scale scatterers. The radar dark Pyroclastic Orientale ring deposits showed both low backscatter and low CPR values, as reported by previous radar observations of pyroclastic deposits. The elevated CPR values corresponding to the interior and exterior of Santos Dumont crater could be attributed to rough crater walls and regional topography, respectively. Finally, attempt was made to bring out the differences in the origin of two similar-sized craters Taylor and Kopff, with the help of SAR polarimetric parameters. Differences in the CPR values of Mare and highland craters were attributed to the sensitivity of CPR to the ilmenite content and presence of surface/sub-surface rocks with diameter of about one-tenth the radar wavelength and larger. This could act as a potential method to distinguish craters of different origin and (or) composition, where the information regarding relative age and regolith composition are not available.

The use of swept-charge devices in planetary analogue X-ray fluorescence studies

The Chandrayaan-1 X-ray Spectrometer (C1XS) was launched onboard the Indian Space Research Organisation (ISRO) Chandrayaan-1 lunar mission in October 2008. The instrument consisted of 24 swept-charge device (SCD) silicon X-ray detectors providing a total collecting area of ∼ 24 cm2, corresponding to a 14° field of view (FWHM), with the ability to measure X-rays from 0.8–10 keV. One algorithm used to analyse the C1XS flight data was developed at Rutherford Appleton Laboratory (RAL) to convert the raw X-ray flux data into elemental ratios and abundances to make geological interpretations about the lunar surface. Laboratory X-ray fluorescence (XRF) data were used to validate the RAL algorithm, with previous studies investigating how the measured XRF flux varies with target surface characteristics including grain size and roughness. Evidence for a grain-size effect was observed in the data, the XRF line intensity generally decreasing with increasing sample grain size, dependent on the relative abundance of elemental components. This paper presents a subsequent study using more homogeneous samples made from mixtures of MgO, Al2O3 and SiO2 powders, all of grain size < 44 μm, across a broader range of mixture ratios and at a higher level of X-ray flux data in order to further validate the RAL algorithm. For the majority of the C1XS flight data analysed so far with the RAL algorithm, the corresponding lunar ground tracks have been generally basaltic, laboratory verification of the algorithm having been primarily conducted using basaltic lunar regolith simulant (JSC-1A) XRF data. This paper also presents results from tests on a terrestrial anorthosite sample, more relevant to the anorthositic lunar highlands, from where the remaining C1XS lunar dataset derives. The operation of the SCD, the XRF test facility, sample preparation and collected XRF spectra are discussed in this paper.

Impact melt in small lunar highland craters

Impact melt deposits have been identified in small, simple impact craters within the lunar highlands. Such deposits are rare, but have been observed in craters as small as 170 m diameter. The melt occurs as well‐defined pools on the crater floor, as well as veneers on the inner crater wall and stringers of material extending over the rim and away from the crater. Model calculations indicate that the amount of melt formed in craters 100–2000 m diameter would amount to a few to ∼106 m3, representing &lt;1% of the crater volume. Thus, significant, visible impact melt deposits would not be expected in such small craters as most of the melt material that was formed would be ejected. Variations in the properties of the projectile or the target cannot account for the amount of observed melt; the amount of melt produced is largely insensitive to such variations. Rather, we suggest that these small melt‐containing craters represent near‐vertical impacts in which the axes of melting and melt motion are essentially straight down, toward the base of the transient cavity. For a given event energy under vertical impact conditions, the volume of melt produced would be greater than in an oblique impact and the momentum of the material would be directed vertically downward with minimal lateral momentum such that most of the melt is retained within the crater interior. Since vertical impacts are relatively rare, such small craters with visible, interior melt deposits are rare. While we focus here on the highlands, such craters also occur on the maria.

Global estimates of lunar iron and titanium contents from the Chang' E‐1 IIM data

Until recently, global high spatial resolution maps of FeO and TiO2 of the Moon were only derived from Clementine data. In this study, we show global maps of FeO and TiO2 using Chang'E‐1 Interference Imaging Spectrometer (IIM) at a spatial resolution of 200 m/pixel. With a newly developed calibration presented here, spectra obtained by IIM compare well with telescopic spectra. Spectral parameters previously shown to be sensitive to iron and titanium, derived from the calibrated IIM data are highly correlated with the measured elemental concentration with R2 = 0.96 for FeO and 0.95 for TiO2. The maps were developed using this calibration. Histograms of basalt FeO estimates have a negatively skewed distribution, while TiO2 distributions are unimodal. They also revealed that the lunar highland crust is relatively uniform on the quadrant scale (several hundred to thousand kilometers scale) but inhomogenous on the global scale. The area of highest elevation of the Moon has very low FeO and TiO2 raising the question about South Pole‐Aitken (SPA) (whether its ejecta deposits covered the highest elevation and when it was formed). Although the average FeO and TiO2 abundances for basalts are highly correlated, local areas of elevated iron can be associated with both high and low titanium.

Conditions of condensate rim formation on the surface of lunar regolith particles

Condensate objects observed in the lunar regolith are distinctly separated on the basis of morpho-logical and chemical characteristics into droplets condensed during the expansion of an impact-generated vapor cloud and films condensed on the relatively cold surface of mineral particles. Using the analyses of both condensate forms and experimental data on the evaporation of melt corresponding to a typical lunar highland rock of the gabbro-anorthosite composition from Apollo 16 sample 68415.40, the temperature conditions of vapor condensation during lunar impact events were estimated. The comparison of condensate compositions with the analyses of vapors from the evaporation experiment showed that, compared with the compositions of droplet-type condensates, the condensate rims were formed from a vapor with high contents of refractory CaO and Al2O3 and at very different condensation temperatures. The enrichment of vapor in CaO and Al2O3 could be attained only at high temperatures of melt evaporation (higher than ∼ 1850°C according to experimental data). The estimated condensation temperatures of droplets are significantly lower, ∼1750–1500°C. Rim-type condensates were produced by vapor quenching on the relatively cold surface of a solid mineral particle, which resulted in almost complete precipitation of all major components of the silicate vapor without fractionation in accordance with their individual volatilities.

The widespread occurrence of high-calcium pyroxene in bright-ray craters on the Moon and implications for lunar-crust composition

[1] We investigated the continuous spectral features of fresh craters on the Moon accompanied by distinctive bright rays, with cavity diameters between 8 and 24 km. We used the data from the Spectral Profiler onboard SELENE (Kaguya) to gain a better understanding of the composition of the lunar highland crust. We found that the observed spectra exhibited strong symmetric absorption around 1 μm and recognizable absorption around 1.3 μm. The spectra around a few craters showed a drastic change in the relative strengths of these two absorption bands s1.3/1.0 at different locations in and around the craters, indicating differences in the abundance of plagioclase and mafic minerals. In contrast, the spectra around most of the craters showed no significant variation in spectral shape, with an essentially constant s1.3/1.0. We analyzed the absorption features of the craters with an essentially constant s1.3/1.0 using the Modified Gaussian Model. We found that the strongest symmetric absorption bands were centered at 0.97–1.01 μm with s1.3/1.0 ≈ 0.2–0.6. Comparing these values with data from known samples, we concluded that high-calcium pyroxene (HCP) is the most plausible dominant mafic mineral identified from the observed spectra. The fact that we detected such HCP-dominant spectra among rayed craters widely spaced across the lunar highland implies that the major mafic component of some portions of the lunar crust is HCP rather than low-calcium pyroxene (LCP).

LUNAR DUST GRAIN CHARGING BY ELECTRON IMPACT: DEPENDENCE OF THE SURFACE POTENTIAL ON THE GRAIN SIZE

The secondary electron emission is believed to play an important role for the dust charging at and close to the lunar surface. However, our knowledge of emission properties of the dust results from model calculations and rather rare laboratory investigations. The present paper reports laboratory measurements of the surface potential on Lunar Highlands Type regolith simulants with sizes between 0.3 and 3 μm in an electron beam with energy below 700 eV. This investigation is focused on a low-energy part, i.e., ≤100 eV. We found that the equilibrium surface potential of this simulant does not depend on the grain size in our ranges of grain dimensions and the beam energies, however, it is a function of the primary electron beam energy. The measurements are confirmed by the results of the simulation model of the secondary emission from the spherical samples. Finally, we compare our results with those obtained in laboratory experiments as well as those inferred from in situ observations.

Making mountains out of a moon

The Moon's cratered surface preserves the record of impacts that occurred during the late stages of its accretion. New simulations show that a collision with a companion moon may have formed the lunar farside highlands. See Letter p.69 The Moon is a satellite of two distinct halves. The nearside that faces us all the time is low in altitude, flat and dark in colour, whereas the farside is mountainous and deeply cratered. Martin Jutzi and Erik Asphaug propose that this lunar dichotomy might be the consequence of the late accretion of a companion moon. Companion moons are a common outcome of giant impact and protolunar disk simulations. The new calculations suggest that a collision with a companion at subsonic impact velocity leads to an accretionary pile rather than a crater, resulting in a hemispheric layer consistent with the dimensions and crustal structure of the topography of the farside highlands.

Preliminary results of TiO2 mapping using Imaging Interferometer data from Chang’E-1

The distribution of titanium abundance on the lunar surface is important knowledge for lunar geologic studies and future resource utilization. In this paper, we develop a preliminary model based on “ground truths” from Apollo and Luna sample-return sites to produce a titanium abundance map from Chang’E-1 Imaging Interferometer (IIM) images. The derived TiO2 abundances are validated with Clementine UVVIS results in several regions, including lunar highlands neighboring the Apollo 16 landing site, and high-Ti and low-Ti maria near the standard site of Mare Serenitatis (MS2). The validation results show that TiO2 abundances modeled with Chang’E-1 IIM data are overestimated for highlands (∼0.7 wt.%) and low-Ti maria (∼1.5 wt.%) and underestimated for high-Ti maria (∼0.8 wt.%).

Remote Sensing Study of Sittampundi Anorthosite Complex, India

In the present study, The Landsat 7 ETM satellite data was collected for the Sittampundi anorthosites complex and digital image analysis was carried out. The anorthositic rocks available at Sittampundi complex is considered as an equivalent of lunar highland rocks. Hence, a remote sensing study comprises of image analysis and spectral profile analysis was carried out. The satellite data was digitally processed and generated various outputs like band combinations, color composites, stretched outputs, and PCA. The suitable processed outputs were identified for delineating the anorthosite complex. The diagnostic absorption features of reflectance spectra are the sensitive indicators of mineralogy and chemical composition of rocks, which are interest to the planetary scientists. The spectral profile of Landsat ETM plotted for pure and mixed anorthosite pixels and compared with the field and lab reflectance spectra. The percentages of image spectra vary from 30% to 60% for Sittampundi anorthosite. The spectral bands 2, 4 and 6 have low reflectance and bands 3 and 5 have high reflectance. The spectral range of bands 2,3,4,5 and 6 are 525 nm–605 nm, 630 nm–690 nm, 750 nm–900 nm, 1550 nm–1750 nm and 10400 nm–12500 nm respectively. The field spectral curve has weak absorptions at 650 nm and 1000 nm due to the iron transition absorption and low ca- pyroxene respectively available in the anorthosite, matching with the image spectra. However, hyperspectal image with narrow bandwidth could be more useful in selecting the suitable spectrum for remotely mapping the anorthosite region, as equivalent test site for lunar highland region.

Geology of the Moscoviense Basin

[1] The Moscoviense Basin, on the northern portion of the lunar farside, displays topography with a partial peak ring, in addition to rings that are offset to the southeast. These rings do not follow the typical concentric ring spacing that is recognized with other basins, suggesting that they may have formed as a result of an oblique impact or perhaps multiple impacts. In addition to the unusual ring spacing present, the Moscoviense Basin contains diverse mare basalt units covering the basin floor and a few highland mafic exposures within its rings. New analysis of previously mapped mare units suggests that the oldest mare unit is the remnant of the impact melt sheet. The Moscoviense Basin provides a glimpse into the lunar highlands terrain and an opportunity to explore the geologic context of initial lunar crustal development and modification.

Analysis on radiative heat transfer between lunar surface and OSR coating

Taking into account the variable radiative properties of the lunar surface and the spectral characteristic of the OSR (Optical Solar Reflector) coating in infrared waveband, a radiative heat transfer computation between the lunar surface and the OSR coating is developed to predict the temperature evolution of the OSR coating. The OSR coating will be used outside of the lunar rover, and the radiative heat transfer is the main way of heat exchange for the OSR coating because there is no air on the Moon. In the process of the temperature computation of the OSR coating, the differential equation of heat conduction in lunar regolith and the orbit law of the Moon are employed to obtain the temperature value of the lunar surface. The simulation results show that the temperature difference of the OSR coating is about 13 K while the lunar rover lands in the lunar mare or the lunar highland, and the gray-body assumption of the OSR coating in infrared waveband should be considered seriously in the radiative heat transfer computation between lunar surface and OSR coating.

Global surface slopes and roughness of the Moon from the Lunar Orbiter Laser Altimeter

[1] The acquisition of new global elevation data from the Lunar Orbiter Laser Altimeter, carried on the Lunar Reconnaissance Orbiter, permits quantification of the surface roughness properties of the Moon at unprecedented scales and resolution. We map lunar surface roughness using a range of parameters: median absolute slope, both directional (along‐track) and bidirectional (in two dimensions); median differential slope; and Hurst exponent, over baselines ranging from ∼17 m to ∼2.7 km. We find that the lunar highlands and the mare plains show vastly different roughness properties, with subtler variations within mare and highlands. Most of the surface exhibits fractal‐like behavior, with a single or two different Hurst exponents over the given baseline range; when a transition exists, it typically occurs near the 1 km baseline, indicating a significant characteristic spatial scale for competing surface processes. The Hurst exponent is high within the lunar highlands, with a median value of 0.95, and lower in the maria (with a median value of 0.76). The median differential slope is a powerful tool for discriminating between roughness units and is useful in characterizing, among other things, the ejecta surrounding large basins, particularly Orientale, as well as the ray systems surrounding young, Copernican‐age craters. In addition, it allows a quantitative exploration on mare surfaces of the evolution of surface roughness with age.

The nature of lunar volatiles as revealed by Mini-RF observations of the LCROSS impact site

[1] On 9 October 2009 the Lunar Crater Observation and Sensing Satellite (LCROSS) impacted Cabeus crater, located near the south pole of the Moon. Prior to that impact, the Mini-RF instruments on ISRO's Chandrayaan-1 and NASA's Lunar Reconnaissance Orbiter (LRO) obtained S band (12.6 cm) synthetic aperture radar images of the impact site at 150 and 30 m resolution, respectively. These observations show that the floor of Cabeus has a circular polarization ratio (CPR) comparable to or less than the average of nearby terrain in the southern lunar highlands. Furthermore, <2% of the pixels in Cabeus crater have CPR values greater than unity. This observation is not consistent with the presence of thick deposits of nearly pure water ice within a few meters of the lunar surface, but it does not rule out the presence of small (<∼10 cm), discrete pieces of ice mixed in with the regolith. In addition, Mini-RF on LRO acquired a postimpact S band image of the region surrounding the LCROSS impact site, providing important geologic context for the site. Registering the LRO image to a near-infrared (NIR) image taken by the LCROSS shepherding spacecraft, we find that the impactor landed in the ray of a fresh, radar-bright, 1 km crater. However, the difference between preimpact and postimpact images is not above the speckle noise. This implies that the size of the LCROSS impact crater is less than Mini-RF's resolution (30 m), and/or that the impact did not excavate more decimeter-size blocks than were already present at the impact site.

Characteristic analysis of the lunar surface and automatically extracting of the lunar morphology based on CE-1

The satellite Chang’E-1(CE-1) was launched in October 24, 2007 in China, which obtained a large number of scientific data of the global moon, including imageries and laser altimetric data. In this paper, the characteristics of the lunar surface are analyzed and the lunar morphologic information of the lunar mare and highland is automatically extracted based on the imagery acquired by CCD camera and the DEM processed by three-line digital photogrammetric technology. The results show that the average elevation of the global moon is -742 m; the highest and lowest locations stand in the farside of the moon; the highest is at the eastern margin of Engel’gardt crater; the lowest is in the secondary impact crater pit of Minkowski crater. The surface of the moon is very flat; most of its slope is bellow 15°, accounting for 90% of the total area of the global moon. The great variation of slope value mainly distributes in the lunar highlands, with an average slope of greater than 7°. The lunar mares widely distribute in the nearside of moon, with an average slope of below 3°. The optimum statistical unit for lunar relief value is 16 km2. The mare and highland are the basic types of lunar morphology, which can be automatically extracted by maximum likelihood classifier based on the elevation data and slope, relief and imagery data. The values of altitude, slope, relief and grey level of CE-1 imageries are normalized and binarized. A case study of H010 (locating in 0°-18°W, 0°-14°S) shows that the overall accuracy assessment for extracted results of the lunar mare and highland based on the geological data published by USGS in 1971 is better, and the Kappa coefficient is 0.78, and the results of the lunar mare and highland show that the method can be used to extract the characteristics of lunar surface.