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High spectral and spatial resolution data from the Moon Mineralogy Mapper (M3) instrument on Chandrayaan-1 are used to investigate in detail changes in the optical properties of lunar materials accompanying space weathering. Three spectral parameters were developed and used to quantify spectral effects commonly thought to be associated with increas...
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... SCREP procedure uses crater depth-to- ejecta thickness relationships to define, in terms of crater radii, an ROI containing the rim and proximal ejecta of an impact crater, which presumably contains the most imma- ture material. We modified the SCREP procedure so that the modeled ROI extends to 5 crater radii from the rim in order Figure 4d but with all spectra scaled to unity at 750 nm. Dashed vertical lines are the wavelengths used for continuum ratio and limits of summation for integrated band depth. ...
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... Figure 3 shows the location of a Mare Serenitatis Crater plotted in Figure 2, along with a radial transect of representative spectra. A similar transect for South Ray Crater, the highlands crater whose maturity trends are illustrated in Figures 1 and 2, is shown in Figure 4. From inspection of Figures 3 and 4, the relation of trends shown in Figure 2 becomes clear. ...
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A new thermal correction model and experimentally validated relationships between absorption strength and water content have been used to construct the first global quantitative maps of lunar surface water derived from the Moon Mineralogy Mapper near-infrared reflectance data. We find that OH abundance increases as a function of latitude, approachi...
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... Following conventions used for Moon Mineralogy Mapper (M 3 ) data (Mustard et al., 2011;Nettles et al., 2011), we characterize the reflectance spectra in terms of their spectral contrast and spectral slope using four parameters: integrated 1 μm band depth, integrated 2 μm band depth, continuum ratio, and albedo (see Section 3.2). We define these parameters in a manner similar to the M 3 analyses, but with adjustments to wavelengths to better match the features in our spectral data. ...
The lunar surface evolves over time due to space weathering, and the visible–near‐infrared spectra of more mature (i.e., heavily weathered) soils are lower in reflectance and steeper in spectral slope (i.e., darker and redder) than their immature counterparts. These spectral changes have traditionally been attributed to the space‐weathered rims of soil grains (and particularly nanophase iron therein). However, understudied thus far is the spectral role of agglutinates—the agglomerates of mineral and lithic fragments, nanophase iron, and glass that are formed by micrometeoroid impacts and are ubiquitous in mature lunar soils. We separated agglutinates and non‐agglutinates from six lunar soils of varying maturity and composition, primarily from the 125–250 μm size fraction, and measured their visible–near‐infrared reflectance spectra. For each soil, the agglutinate spectra are darker, redder, and have weaker absorption bands than the corresponding non‐agglutinate and unsorted soil spectra. Moreover, greater soil maturity corresponds to darker agglutinate spectra with weaker absorption bands. These findings suggest that agglutinates (rather than solely the space‐weathered rims) play an important role in both the darkening and reddening of mature soils—at least for the size fractions examined here. Comparisons with analog soils suggest that high nanophase iron abundance in agglutinates is likely responsible for their low reflectance and spectrally red slope. Additional studies of agglutinates are needed both to more comprehensively characterize their spectral properties (across size fractions and in mixing with non‐agglutinates) and to assess the relative roles of agglutinates and rims in weathering‐associated spectral changes.
... An additional absorption feature located near 2.20 µm in the image spectra may indicate the presence of some clay mineral along with calcite. The image spectra show a relatively higher continuum slope than the library spectra that may indicate differences in weathering [70], which generally mantles the uppermost surface of rocks, differences in geometry of data acquisition or may be related to presence of mineral mixtures. The overall shape of the major absorption feature near 2.33 µm of the image and the library reflectance spectra of calcite (Figure 5a) is in accordance, although a minor absorption feature near 2.12 µm seen in the library spectra is absent in the image spectra. ...
... An additional absorption feature located near 2.20 µm in the image spectra may indicate the presence of some clay mineral along with calcite. The image spectra show a relatively higher continuum slope than the library spectra that may indicate differences in weathering [70], which generally mantles the uppermost surface of rocks, differences in geometry of data acquisition or may be related to presence of mineral mixtures. ...
Talc deposits of Jahazpur, Rajasthan, hosted by dolomite, are one of the largest high-quality talc deposits in India. In the present study, we use AVIRIS-NG datasets to study the link between the spatial pattern of talc mineralization, associated alteration minerals, and iron-oxide enrichment. It is noted that the majority of talc-bearing areas are characterized by the presence of clay minerals, such as an intimate mixture of kaolinite and muscovite, illite, dickite (indicative of phyllic and argillic alteration), and also enhanced iron enrichment. The talc-bearing zones are located adjacent to quartz-rich lithologies, and they are aligned along the Jahazpur thrust. Based on mineralogical and geological evidence, hydrothermal alteration of dolomites by silica and iron-rich fluid is proposed as major factorcontrolling talc mineralization. This study has implications for the identification of prospective zones of talc mineralization using imaging spectroscopy.
... The OMAT parameter gauges the darkening and reddening effects of submicroscopic metallic iron (SMFe, sometimes referred to as nanophase iron or nanosize iron), which is created in lunar regolith as a consequence of space weathering by micrometeoroid impacts and solar-wind exposure (e.g., Hapke, 2001;Pieters et al., 2000). Variants of the Lucey compositional and OMAT algorithms have been developed for spacecraft spectral datasets that have similar wavelength coverage to that of the original Clementine data (e.g., Coman et al., 2018;Nettles et al., 2011;Otake et al., 2012;Sato et al., 2017;Sun et al., 2016;Wu et al., 2012). ...
We explore the extent to which red‐green‐blue (RGB) color images, such as those produced by a complementary metal oxide semiconductor (CMOS) Bayer‐filter camera, can be utilized for studying the maturity and composition of the lunar surface. RGB filters typically are quite broad, with considerable overlap among the three colors. Convolution of laboratory spectra for lunar samples to the RGB responsivities of the Chang'E‐3 rover's Panoramic Camera allowed determination of the correlations between color ratios (B/R, B/G, and G/R) and the sample maturity (Is/FeO) or composition (wt.% FeO or TiO2). In general, color ratios decrease as Is/FeO increases. When separate sample categories are considered, we find that the B/R ratio is a good predictor of Is/FeO for low‐Ti mare, low‐Fe highland, and moderate‐Fe highland soils. For high‐Ti mare soils, Is/FeO has little influence on the B/R ratio (due to the spectral effects of abundant ilmenite), and hence the ratio cannot be used to determine maturity. We also find that color ratios have no useful correlation with sample wt.% FeO or TiO2. Thus, in locations excluding the high‐Ti maria, RGB color data could be used to estimate soil maturity. We outline a concept for a multispectral imager based on a CMOS sensor with a Bayer‐like pattern of custom‐wavelength filters chosen specifically for lunar science applications.
... Therefore, in some cases, mature soil may have the identical optical maturity parameter (OMAT) value as that of an immature exposure. Similarly, Nettles et al. (2011) endorses the same concept during the quantification of spectral variation with the maturity trend of M 3 observation. Eventually, it is clear that a classification of optical maturity trend alone cannot efficiently highlight the mineralogical anomalies but can characterize the background based on the optical properties. ...
... However, this analysis can hold the criteria for immature pixels containing below 10% of the maximum point density. Nettles et al. (2011) proposed that the maturity trend of the lunar surface can be mapped by the M 3 observation consistently, using several maturity measurements such as continuum ratio vs. 1579-nm reflectance (albedo), continuum ratio vs. integrated 1000nm band depth and reverse integrated 1000-nm band depth vs. 1579-nm reflectance (albedo) scatter plot. The corresponding plotting parameters have been defined in the following way, where R = reflectance of a spectrum and R c =continuum removed reflectance of a spectrum: ...
... (3) Nettles et al. (2011) mainly studied various lunar ROIs to visualize the corresponding maturity trends in scatter plot (see Figure 2). However, it can be stated that each type of lunar soil can have its own starting and ending point in the maturity trend and can have a unique pathway under the different compositional susceptibility. ...
The mineralogical anomaly is the mineralogically diagnostic character that differs from its surrounding spectra in terms of absorption features of a spectrum. On the airless planetary body like our Moon, the characteristics of mineral exposures are mostly affected by the physical process over time because of space weathering. This inevitable fact produces mature exposures that act as a background for mineralogical anomaly detection. In this regard, the present study categorizes the optical maturation trend of a site, and the background characterization is integrated with anomaly detection, which makes it more practical, robust, and efficient. These fundamental ideas have been improvised into our automated mineralogical anomaly detection method that uses a modified density-based spatial clustering of applications with noise (Modified DBSCAN) algorithm to categorize the maturity trend from various scatter plots of spectral property. Subsequently, the Reed-Xiaoli detector analyzes the data points belonging to below 33% of maximum point density on the corresponding scatter plot. Experimentally, the proposed method has been validated with previously reported results of literatures over the varietal lunar sites (crater Theophilus, crater Humboldt, Hansteen Alpha silicic dome, western inner ring of Mare Moscoviense, and crater Von Kármán), which have diverse mineralogy in the region. The reflectance spectra of anomalous points explore the mineralogical diversity of the studied region using Chandrayaaan-1 Moon Mineralogy Mapper (M3) data. However, it can also operate with any hyperspectral datasets within the spectral range of 400–3000 nm. This flexibility makes our proposition more attractive for an end-user in the field of planetary science.
... Notably, the Diviner rock abundance proximal to dated craters exhibits a tight correlation with crater age, constraining the mechanical weathering of surface rocks and providing a new chronometer used to date similarly rocky craters (Ghent et al., 2014;Mazrouei et al., 2019). Constraining the optical weathering rate of the regolith has proven more challenging, partially due to target composition biasing optical maturity parameters, inhibiting global comparisons (Braden & Robinson, 2013;Grier et al., 2001;Nettles et al., 2011). ...
Plain Language Summary
The Moon, Mercury, and asteroids lack protective atmospheres and slowly darken over time due to their exposure to space. We call this darkening process space weathering. Apollo samples returned from the Moon show that space weathering produces tiny iron particles that range in size from nanometers to micrometers. We use orbital lunar maps of nanophase and microphase iron content to better understand how quickly space weathering occurs on the Moon. We first find the iron content of young lunar soils deposited by large impact events, then use the age of each impact crater to see how much iron accumulates in different lengths of time. We find that nanophase iron accumulates predictably over time due to space weathering. In contrast, microphase iron accumulates less predictably, possibly because it exists in the lunar soil initially, or is delivered to the Moon by crater‐forming impacts. This work helps us understand how the surface of the Moon weathers over time and how space weathering might work elsewhere in the Solar System.
... Where R750 is the reflectance at 750nm of a pixel or spectrum, and R950 is the reflectance at 950nm of a pixel or spectrum (Figure 2c and Figure 3c). The constants R0 and R1 apply to Clementine data only and must be used with the Clementine datasets (Baronia & Sarup, 2019;Lucey, Taylor, & Hawke, 1998;Nettles et al., 2011). Constants for M 3 datasets of the Apollo 17 landing site have been obtained by plotting the graph between R950/R750 and R750, i.e., 0.04,1.08. ...
... These trends represent space weathering effects-band Depths Vs. Band Slopes trends separate the Mare and Highlands regions (Nettles et al., 2010(Nettles et al., , 2011. For the shoemaker crater, larger the depth, higher the slope. ...
The upcoming Artemis mission of NASA is planned to land humans within 6 degrees of the lunar South Pole. This work analyzes spectral parameters obtained from hyperspectral dataset from Moon Mineralogy Mapper of Chandrayaan-1, to characterize the Shoemaker crater in the lunar south pole region as one of the landing sites for the Artemis III mission. There is a possibility of cold water traps in this crater as it is one of the permanently shadowed areas and falls within 6 degrees of the south pole. Few expected differences and some interesting spectral features obtianed after comparing the spectra for shoemaker crater and Hutton impact crater (far side) and Le Verrier, a lunar impact crater on the north of the Mare Imbrium (near side). The spectral trends also depict that these regions have so much to provide for earlier lunar dynamo. The extraction of hydrogen from the bottom of the craters in the lunar south pole and its analysis for cosmic bombardment can be one of the Artemis III mission's science objectives.
... Three parameters were used: the 1578 nm reflectance band (for reduced albedo, A), a continuum slope (for increased reddening, C), and an integrated band depth ratio (for attenuation of diagnostic absorption band depth, I). Contrary to employing a simple ratio as in [29], C scales the slope of a straight line passing through the UVVIS and NIR spectra of the M 3 data. ...
The Moon has a large potential for space exploration and mining valuable resources. In particular, 3He provides rich sources of non-radioactive fusion fuel to fulfill cislunar and Earth's energy demands, if found economically feasible. The present study focuses on developing advanced techniques to prospect 3He resources on the Moon from multi-sensor remote sensing perspectives. It characterizes optical changes in regolith materials due to space weathering as a new retention parameter and introduces a novel machine learning inversion model for retrieving the physical properties of the regolith. Our analysis suggests that the reddening of the soil predominantly governs the retention, along with attenuated mafic band depths. Moreover, semi-variograms show that the spatial variability of 3He is aligned with the episodic weathering events at different timescales. We also observed that pyroclastic regoliths with high dielectric constant and increased surface scattering mechanisms exhibited a 3He abundant region. For ejecta cover, the retention was weakly associated with the dielectric contrast and a circular polarization ratio (CPR), mainly because of the 3He-deficient nature of the regolith. Furthermore, cross-variograms revealed inherent cyclicity attributed to the sequential process of weathering effects. Our study provides new insights into the physical nature and near-surface alterations of lunar regoliths that influence the spatial distribution and retention of solar wind implanted 3He.
... The Moon Mineralogy Mapper (M 3 ) spectra can be used to identify fresh craters, as shown by Nettles et al. (2011). They used the spectra to evaluate the maturity trends in fresh craters and their rays. ...
... Although the authors admit that the correction has its simplifications and should be improved in the future, we still find the data appropriate for our research, because the trends we found are valid for each swirl separately (viewed under only one geometry). The same argument has been used by Nettles et al. (2011) for example. They suggested that spectral changes are not only a function of maturity, but local mineralogy also plays some role. ...
Higher magnetic field in lunar swirls is believed to deflect majority of incoming charged particles away from the lunar-swirl surfaces. As a result, space weathering inside and outside swirls should be different. We wanted to evaluate these differences, therefore we have examined seven swirl areas on the Moon (four mare and three highland swirls). We applied the Modified Gaussian Model to statistical sets of the Moon Mineralogy Mapper spectra. Using Principal Component Analysis (PCA), we were able to distinguish the old (weathered) material from both the fresh crater and swirl materials. The swirls did not follow the same behavior as the fresh material, nor were they fully separable. Additionally, we could distinguish between the mare and highland swirls (mare/highland dichotomy) based on the PCA and histogram plots of the albedo and strength of the 1000-nm absorption band. The mare/highland dichotomy can partially be caused by different FeO content in maria and highlands, which points to the existence of a threshold value that changes the spectral evolution due to space weathering. Slope behavior seemed to be dependent on whether the swirl was on the near- or far-side of the Moon, likely due to shielding of lunar nearside by Earth's magnetotail. Our results thus favor the solar wind stand-off hypothesis in combination with the fine dust transport hypothesis and point to the fact that micrometeoroid impacts generally do not reproduce the same weathering trends as all the space weathering effects together.
... The more mature regolith is characterized with finer crystalline grain as compared to that of the coarsely grained immature soil. Several maturity models have been developed for quantifying the changes in the spectral properties of the regolith due to the interaction of space weathering agents like solar wind, galactic cosmic rays, and meteorites [17]- [20]. The maturity model proposed by Lucey and coworkers utilizes the Clementine's UVVIS 750 and 950 nm spectral reflectance bands, denoting the ferrous electronic absorptions [17]. ...
... Alternatively, a qualitative approach has been developed by incorporating the spectral changes due to space weathering agents and producing a high-resolution maturity color composite through Chandrayaan-1 Moon Mineralogy Mapper (M 3 ) observations [20]. Eventually, one of the effects of space weathering is the increase of mafic absorption band depth with the decrease in the size of regolith grain. ...
... The M 3 spectroscopy is further extended toward quantifying the effects of space weathering on the spectral properties of the lunar soil. The variations in the maturity within the study area are investigated by using the Nettles model [20]. In this, a color composite image is generated by considering the following spectral parameters: Albedo (1548 nm), IBD1000 (Integrated Band Depth at 1000 nm, for reduced absorption band depth effect) and continuum ratio (1508/730 nm, representing the spectral reddening). ...
The enigmatic swirls of Reiner Gamma Formation (RGF) have been found to be associated with localized magnetic surges and high albedo markings. The intriguing diversity within deep-seated lithologies unravels the compositional evolution of the RGF soil, thereby providing new insights into the geological formation of lunar swirls. The present work contributes to the petrophysical significance of possible mafic units by utilizing the multisensor data from recent lunar missions. The compositional characterization of mafic-rich regolith facilitates an improved high-resolution eigenvector-based pyroxene spectroscopy. This provides evidence of endogenic magmatic water in the spectra of high Mg orthopyroxene with pronounced olivine content. Some regions in the western part contribute to the presence of chromium with the possible emplacement of mafic-rich basalts in the oxygen-deficient environment. The sensitivity of the radar echo to the petrographic units has been utilized to derive the physical characteristics of the regolith grains. The regions with enhanced hydration attribute to an increased dielectric permittivity with an associated surge in bulk density and circular polarization ratio. This is in concordance with the degree of maturity in the regolith due to space weathering. Moreover, a relatively compact confinement of the soil pattern has been observed in the immature mafic-rich patches, emphasizing the mechanical stability of the regolith. The regional geomorphology indicates the emanation of wrinkled ridges, wherein higher mafic abundance zone attributes to the primitive source of extruded magma. In essence, this study proposes the inclusion of local charged dust variant in the global formation perspective of the RGF.
... This technique is mainly valid for middle to high latitude regions where there are brightness variations due to local topography. Apart from this, the potential of Chandrayaan-1 M 3 data has been assessed by examining the optical maturity trends for regional regoliths (Nettles et al., 2011). This can be qualitatively described in terms of nanophase iron induced spectral effects. ...
... This can be qualitatively described in terms of nanophase iron induced spectral effects. Furthermore, the scatterplots of the associated parameters reveal the space weathering trends for crystalline inclusions of ejecta and fresh craters (Nettles et al., 2011). In principle, three spectral parameters are derived representing the impacts of space weathering on lunar soil. ...
... Contrary to employing simple ratio as in Nettles et al. (2011), the present study integrates the UVVIS and NIR spectra of the M 3 data and scales the slope of the straight line passing through them as The quantitative measure of continuum slope (CS, in µm -1 ) for a regolith grain increases with the enhanced exposure time to the space environment. This reflects the inclusion of nanophase metallic iron fragments influencing the spectral behaviour of the grain. ...
The Moon serves as an attic to the Earth’s treasure by preserving the volatile repository from the harsh space environment. The exposure of the lunar surface to the solar wind plasma results in the implantation of potential 3He into the top 1 mm of the regolith. The retention of the 3He primarily depends on the regional ilmenite content and maturation subject to the solar wind plasma supply. In the present research, an attempt is made to explore the influence of petrophysical properties of the regolith on the retained 3He using multisensor approach. The retention framework is improved by incorporating the associated effects of space weathering on the regolith materials, which are represented by spectral parameters. The integration of the spectral parameters, plasma flux, and ilmenite content leads to a novel hybrid variable that is directly compared with the in-situ 3He measurements at the Apollo and Luna landing sites. Considering the independence of the space weathering processes, the correlation analysis suggests that the predicted 3He contents are in close agreement with the actual abundance. However, all the weathering processes lead to the reduction of Fe2+ into the nanophase metallic iron particles, thereby interrelating to each other. The applicability of the weighted average linear combination is utilized to model the unknown inherent relationship between the weathering trends. Upon comparing with the in-situ 3He, the RMSE reduces to 1.17 ppb compared to the independent approach. The empirical relationship is applied to the Vallis Schroteri region, wherein the high 3He abundant regions emerge out to be pyroclastic deposits and localized hotspots near the primary rille and Agricola Mountains. It is also observed that the two dominant processes governing the abundance are attenuation of the mafic absorption band depths and reddening of the soil. However, a different scenario all together appears for the 3He abundance per unit area, wherein the soil chemistry proves to be a deciding factor. The spatial variability of the 3He abundant regolith is found to be aligned with the episodic space weathering events over the geological timescale, clearly indicated by the cyclic behaviour of the variogram trends. Moreover, the highly retained 3He content may be oriented at around 135º relative to other directions. The lower cutoff and width increases the spatial variability of the deposition. The retention of the 3He is found to be associated with the petrophysical properties of the soil. This is clearly illustrated by comparing the retrieved scattering mechanisms, dielectric content, and geotechnical variations. In the research, the utility of the radar backscatter is modelled as a function of incidence angle, dielectric constant and surface roughness. The sensitivity analysis is performed, which provides the bounding limits of the realistic surface parameters and radar configuration. This is fed into the multilayer perceptron neural network for performing the inversion based on multivariate regression. The inverted dielectric constant shows an RMSE of 0.26. The retrieval process is applied to the monostatic data of the landing sites, wherein the inverted values are in close agreement with the actual values. Upon testing the study site, the pyroclastic regoliths are associated with high dielectric constant and increased surface scattering mechanisms. The regolith is also characterized by lower void spaces between the grains and higher relative density. Due to the freshly formed microcraters, the excavation of the rocks from the interior lowers the penetration of the radar wave, thereby increasing the granular packing of the gardened regolith. As the dielectric contrast increases, the retention of the lower 3He ejecta regolith increases, attributing to the roughness variations. The observation is also aligned with the CPR. Moreover, the abundance is negatively correlated with the void ratio for shorter lag distances. On the contrary, the higher abundant pyroclastic regolith relates well with the surface scattering mechanisms associated with cyclicity. An opposition is also observed in this to the bistatic angle with a more significant exponential depth profile. Furthermore, retention modelling provides new insights into the potential mining operations for the lunar outposts. The study recommends deeper exploration of the pyroclastic regoliths, thereby contributing to the lunar mining and remote sensing paradigms.
