Chandrayaan-1 Moon Mineralogy Mapper Research Articles

Chronology, composition, and mineralogy of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum

The timeline of volcanic activity is critical for constraining the thermal evolution of the Moon. The spatial extents of mare basalts, major products of lunar volcanism, have been precisely extracted from LROC (Lunar Reconnaissance Orbiter Camera) image mosaics. With the maria extents newly extracted from LROC mosaics, we found that a large area of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum (the PIV region) has not yet been dated. This study analysed the chronology, composition, and mineralogy of the PIV region, aiming to finish the picture of basaltic volcanism in the Procellarum region, which is a key puzzle of our global geological mapping of the Moon. According to the topographical, spectral, and compositional characteristics, mare units of the PIV region are defined, and the crater size frequency distribution is measured. The primary craters with diameters >0.1 km in the PIV region are measured, and the absolute model ages of basalt units between ∼3.78 Ga and ∼1.71 Ga are derived. Most western PIV basalt units are Eratosthenian-aged, while eastern units mostly formed in the Imbrian period. The spectra of 4965 small impact craters are extracted to interpret the mineral compositions of the PIV basalt units using Chandrayaan-1 Moon Mineralogy Mapper data. Using a Modified Gaussian Model, the reflectance spectra are deconvoluted, and the obtained modal proportions of mafic minerals show low olivine and high low-Ca pyroxene abundances in the eastern PIV region, while the western region features high olivine and calcic pyroxene concentrations. Three episodes of volcanic events occurring in the PIV region are identified. The first (main) occurred at approximately 3.5 Ga (Late Imbrian), with erupted lava flows with less evolved compositions covering most of the PIV area. The peak of volcanic activity in the Eratosthenian period occurred around 2.5 Ga, where mare basalts with moderately evolved compositions and mineralogy were formed. The last major eruption occurred at approximately 1.8 Ga, forming mare basalts with highly evolved compositions.

Possible Formation Mechanism of Lunar Hematite

Hematite, a ferric mineral with diagnostic features in the visible and infrared spectral range, has recently been discovered in the polar regions of the Moon by the Chandrayaan-1 Moon Mineralogy Mapper (M3). The oxygen involving the oxidization process producing lunar hematite is supposed to originate from the Earth’s upper atmosphere, and hematite with different ages may have preserved information on the oxygen evolution of the Earth’s atmosphere in the past billions of years. The discovery of lunar hematite may provide insight into the understanding of the oxidation products on the Moon and other airless bodies. In this work, we analyze hematite abundance distribution in the lunar polar regions, showing that the content of hematite on the lunar surface increases with latitude, and is positively correlated with surface water abundance. We suggest that the latitude dependence of hematite is derived from the latitude dependence of water, which indicates that water may play an essential role in the formation of hematite. The correlation between hematite and the optical maturity parameter (OMAT) was analyzed and a significant positive correlation was observed, which suggests that the hematite in the polar regions is the result of gradual and persistent oxidation reactions. In addition, based on the analysis of oxygen particles in the Earth wind, it was found that O+ and O2+ are much more abundant, suggesting that low-energy O+ or O2+ ions escaping from the upper atmosphere of the Earth may play a crucial role in the formation of hematite in the lunar polar regions.

Petrological and Mineralogical Characteristics of Exposed Materials on the Floors of the Lavoisier and Surrounding Craters

Five floor-fractured craters (FFCs), Lavoisier crater and four craters surrounding it (Lavoisier C, Lavoisier E, Lavoisier F, and Lavoisier H), are distributed along the boundary between the northwestern part of the Oceanus Procellarum and the highlands. This study examines the uplifted or exposed materials on the fractured floors of these five impact craters using petrological, mineralogical, and morphological analyses. We inferred the processes that uplifted or exposed the materials from the subsurface to the crater floor using the Chandrayaan-1 Moon Mineralogy Mapper (M3) level 1b (thermally and topographically corrected spectral radiance) data and level 2 (spectral reflectance) data. The elemental abundances, petrological, and mineralogical characteristics of the study regions were mapped. We confirm that mare basalts and dark mantle deposits exist on the floors of these five craters. These two materials (mare basalts and dark mantle deposits) were used to identify minerals exposed on the floor surface of craters using spectral reflectance spectra. Two mineral groups were identified: pigeonite (or orthopyroxene in norite (low-Ca pyroxene) occurred in the craters Lavoisier, Lavoisier F, and Lavoisier H, and subcalcic augite (high-Ca pyroxene) occurs in the craters Lavoisier C and E. Our approach demonstrates that the characterization of uplifted or exposed surface minerals using elemental maps, spectral parameter composite maps, and reflectance spectra can provide information critical for prospective studies involving lunar geology and in situ resource utilization.

New view of the Balmer-Kapteyn region: Cryptomare distribution and formation

Context. The cryptomare in the Balmer-Kapteyn region is the oldest one on the Moon. Determining the extent and formation of this feature can deepen our understanding of early mare volcanism and help establish temporal and spatial constraints on lunar thermal and volcanic history. Aims. This paper focuses on the identification of lunar cryptomaria and figuring out their formation processes. Methods. We used the Global WAC digital terrain model to analyze the terrain. We built a mathematical model using support vector machines and input Kaguya Multiband Imager data to estimate oxide concentrations in the Balmer-Kapteyn region. We used the Chandrayaan-1 Moon Mineralogy Mapper (M3) to analyze the minerals. We improved the cryptomare identification model to increase the accuracy of basalt identification in the cryptomare region. Finally, we used three methods to estimate the ejecta thickness of the target basin to the Balmer-Kapteyn region. Results. New Al2O3, CaO, FeO, MgO, and TiO2 maps were generated using the Kaguya Multiband Imager and a novel machine-learning model. As a result, the extent of the cryptomare in the Balmer-Kapteyn region was redefined and the formation process of the cryptomare in the Balmer-Kapteyn region was divided into five formation stages: Balmer basin formation, ejecta coverage from the Pre-Nectarian and Nectarian large impact basins, mare basalt filling, ejecta secondary coverage of high-albedo materials, and exposure of mare basalts. Conclusions. We found that the bottom of the Crater Vendelinus is likely to hide ancient mare basalt. Moreover, the high-aluminum mare basalt of the cryptomare is different from the composition of the exposed mare basalts in Mare Fecunditatis and Crater Vendelinus. The high-albedo material covering the cryptomare in the Balmer-Kapteyn region could have come from the Langrenus, Petavius, Humboldt, La Perouse, and Ansgarius Craters, along with some from the Orientale Basin impact event or potentially from the Imbrium Basin impact event.

The Scientific Value of a Sustained Exploration Program at the Aristarchus Plateau

Abstract The Aristarchus plateau hosts a diversity of volcanic features, including the largest pyroclastic deposit on the Moon, the largest sinuous rille on the Moon, and intrusive and extrusive examples of evolved, Th-rich silicic lithologies. We provide an overview of previous remote-sensing measurements of the Aristarchus plateau and provide new analyses of Diviner Lunar Radiometer thermal IR data, Lunar Prospector Gamma Ray Spectrometer Th data, Chang’e-5 Microwave Radiometer data, and hyperspectral and multispectral visible/near-infrared images and spectra from the Chandrayaan-1 Moon Mineralogy Mapper and the Kaguya Multispectral Imager. The rich diversity of volcanic features on the Aristarchus plateau presents an opportunity for a sustained science and exploration program. We suggest a series of missions to the Aristarchus crater floor or ejecta, the Cobra Head, and Herodotus Mons to investigate the link between pyroclastic, effusive basaltic, and silicic volcanism in the region. Such missions would enable analyses of silicic rocks that are rare in the Apollo sample collection and demonstrate in situ resource utilization of FeO- and H2O-bearing pyroclastic materials.

Spectral properties of lunar impact melt deposits from Moon Mineralogy Mapper (M3) data

Lunar impact melt deposits have unusual surface properties, unlike any measured terrestrial lava flow. Radar observations suggest that they are incredibly rough at decimeter scales, but they appear smooth in high-resolution, meter-scale optical images. The cause of their unusual surface roughness is unknown. In this work, we investigate the properties of impact melt deposits from seven lunar craters, ranging in size from 7.5 to 96 km in diameter, in an effort to understand the cause of their unique surface texture. We use data from the Lunar Reconnaissance Orbiter's (LRO) Mini-RF instrument to characterize the small-scale roughness of the deposits, data from the LRO Camera (LROC) to characterize their meter-scale morphology, and data from Chandrayaan-1's Moon Mineralogy Mapper (M3) to characterize their composition. This represents the most comprehensive study of the composition of lunar melt deposits completed to date. In particular, we applied a customized spectral unmixing model to the M3 data using laboratory spectra acquired from a range of possible lunar endmembers: pyroxene, olivine, fast-quenched lunar glass simulants, and impact melts and breccias (both synthetic and natural). We found that spectra derived from lunar melt deposits are typically modeled as a mix of the pyroxene and/or impact melts and breccias endmembers. Our modeled results suggest that lunar melt deposits are either crystalline deposits of pyroxene-rich rocks, or a mixture of glassy material and pyroxene minerals. The latter interpretation could explain the roughness observed in the Mini-RF data, if the melt deposits have a glassy surficial layer that shatters during impact gardening to produce decimeter scale blocks.

Earth Wind as a Possible Exogenous Source of Lunar Surface Hydration

Abstract Understanding the sources of lunar water is crucial for studying the history of lunar evolution, as well as the interaction of solar wind with the Moon and other airless bodies. Recent orbital spectral observations revealed that the solar wind is a significant exogenous driver of lunar surficial hydration. However, the solar wind is shielded over a period of 3–5 days per month as the Moon passes through the Earth’s magnetosphere, during which a significant loss of hydration is expected. Here we report the temporal and spatial distribution of polar surficial OH/H2O abundance, using Chandrayaan-1 Moon Mineralogy Mapper (M 3) data, which covers the regions inside/outside the Earth’s magnetosphere. The data shows that polar surficial OH/H2O abundance increases with latitude, and that the probability of polar surficial OH/H2O abundance remains at the same level when in the solar wind and in the magnetosphere by controlling latitude, composition, and lunar local time. This indicates that the OH/H2O abundance in the polar regions may be saturated, or supplemented from other possible sources, such as Earth wind (particles from the magnetosphere, distinct from the solar wind), which may compensate for thermal diffusion losses while the Moon lies within the Earth’s magnetosphere. This work provides some clues for studies of planet–moon systems, whereby the planetary wind serves as a bridge connecting the planet with its moons.

Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls

We investigated six bright swirls associated with magnetic anomalies of variable strength using Chandrayaan-1 Moon Mineralogy Mapper (M3) hyperspectral image data. We examined the 3 μm absorption band generally ascribed to solar wind-induced OH/H2O and spectral trends in the near-infrared wavelength range at on-swirl and off-swirl locations. We found that the 3 μm absorption band is weaker at on-swirl than at off-swirl locations and shows only weak variations with time-of-day. This result is consistent with magnetic anomaly shielding that reduces solar wind interaction with the surface. For a small swirl structure in Mare Moscoviense, we found the 3 μm absorption band to be similar to that of its surroundings due to the absence of strong magnetic shielding. Our spectral analysis results at on-swirl and off-swirl locations suggest that the spectral trends at on-swirl and off-swirl locations cannot always be explained by reduced space-weathering alone. We propose that a combination of soil compaction possibly resulting from the interaction between the surface and cometary gas and subsequent magnetic shielding is able to explain all observed on-swirl vs. off-swirl spectral trends including the absorption band depth near 3 μm. Our results suggest that an external mechanism of interaction between a comet and the uppermost regolith layer might play a significant role in lunar swirl formation.

Lithological mapping of Eratosthenes crater region using Moon Mineralogy Mapper of Chandrayaan-1

Selenological exploration (lunar geology) involves mapping and delineation of different rock types and minerals present in the Moon. Various lunar missions with multi-spectral sensors provided preliminary information about the lithological and mineralogical occurrences on the Moon. The Chandrayaan-1 Moon Mineralogy Mapper (M3), provided hyperspectral data having high spatial resolution of 140 ​m and 85 continuous spectral bands of Electro Magnetic Spectrum from 430 to 3000 ​nm. This data utilized for identification of distinctive absorption bands near 1000, 1250, 2000 and 2500 ​nm regions. These absorption features are playing vital role in mapping of various minerals and rock types on the lunar surface with higher precision. The present study aimed to map the compositional diversity in and around the Eratosthenes crater region of the lunar surface using M3 data of Chandrayaan-1. The initial studies carried out using Clementine ultraviolet and visible (UVVIS) warped color-ratio mineral map and M3 data based band shape, band depth and band ratio algorithms have led to understand the lithological diversity of the study area. These preliminary studies revealed that the Eratosthenes crater region contains mare basalt, anorthosite, highland soil, pyroxene, Olivine, etc. At the next stage, the detailed compositional variability of the study area was analyzed using Spectral Information Divergence (SID) algorithm using various thresholds. Finally, The SID analysis showed that the spatial distribution of olivine, pigeonite, augite and norites present within the study region. The present study further revealed that the SID could be an effective detection tool rather than as a classification tool.

Detection of an excessively strong 3-μm absorption near the lunar highland crater Dufay

Using the near-infrared spectral reflectance data of the Chandrayaan-1 Moon Mineralogy Mapper (M3) instrument, we report an unusually bright structure of 30 × 60 km2 on the lunar equatorial farside near crater Dufay. At this location, the 3-μm absorption band feature, which is commonly ascribed to hydroxyl (OH) and/or water (H2O), at local midday is significantly (∼30%) stronger than on the surrounding surface and, surprisingly, stronger than in the illuminated polar highlands. We did not find a similar area of excessively strong 3-μm absorption anywhere else on the Moon. A possible explanation for this structure is the recent infall of meteoritic or cometary material of high OH/H2O content forming a thin layer detectable by its pronounced 3-μm band, where a small amount of the OH/H2O is adsorbed by the surface material into binding states of relatively high activation energy. Detailed analysis of this structure with next-generation spacecraft instrumentation will provide further insight into the processes that lead to the accumulation of OH/H2O in the lunar regolith surface.

A GENERIC RIGOROUS SENSOR MODEL FOR PHOTOGRAMMETRIC PROCESSING OF PUSHBROOM PLANETARY IMAGES

Abstract. Currently, each planetary exploration mission team always develops its own software modules to support the photogrammetric processing of planetary images, and as a result of that the main drawbacks are lacking software reusability and the high cost of software development and maintenance. This is mainly due to that there is lack of a highly universal sensor model in the planetary mapping community. This paper presents a generic rigorous sensor model (RSM) for the photogrammetric processing of pushbroom planetary images. The main contributions of this paper include: (1) the implementation details of the generic RSM; (2) the optimized coordinates transformation methods between 3D ground points and 2D image points for linear pushbroom images; (3) a pipeline to acquire exterior orientation (EO) parameters for each planetary image. The generic RSM is developed based on the methodology used in airborne linear scanners ADS40. Specifically, the generic RSM comprises of a camera file and an orientation data file for each image. The camera file stores each detector’s calibrated image coordinates and the orientation data file contains each scan line’s EO parameters, such that the RSM can perform coordinates transformation among pixel coordinates, focal plane coordinates and ground coordinates. Furthermore, the generic RSM supports varying exposure time, summing mode and image distortions, which are typical problems that need to be solved in planetary mapping. We tested the generic RSM with Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC), Chandrayaan-1 Moon Mineralogy Mapper (M3) and Mars Express (MEX) High Resolution Stereo Camera (HRSC) images. The geometric accuracy and computational efficiency of the developed generic RSM were compared with the famous planetary mapping software, namely Integrated System for Imagers and Spectrometers (ISIS). The experimental results demonstrate that the generic RSM has the merits of processing various types of pushbroom planetary images with a unified way and decreasing the software development and maintenance burden. Moreover, the developed generic RSM significantly improves the computational efficiency of orthophoto generation and tie points extraction for pushbroom planetary images.

Revisiting the field geology of Taurus–Littrow

Integration of Apollo 17 field observations and photographs, sample investigations, Lunar Reconnaissance Orbiter Camera images, Chandrayaan-1 Moon Mineralogy Mapper (M3) spectra, and Miniature Radio Frequency (Mini-RF) S-band radar images provides new insights into the geology of the valley of Taurus–Littrow on the Moon. Connecting the various remote observations to sample data enables a set of new conclusions to be drawn regarding the geological evolution of the valley. Structural considerations and published and recalculated 40Ar/39Ar analyses of samples from the North Massif and the Sculptured Hills indicate that the Crisium basin formed about 3.93 Ga; the Serenitatis basin about 3.82 Ga; and the Imbrium basin no earlier than 3.82 Ga and no later than the average of 3.72 Ga for 33 age dates from samples of the valley's mare basalts. Strong evidence continues to support the conclusion of others (Lucchitta, 1972; Spudis et al., 2011; Fassett et al., 2012) that the Sculptured Hills physiographic unit consists of Imbrium ejecta. Interpretation of M3 spectral data and Apollo 17 samples indicate that rock units of the Sculptured Hills consist of a largely coherent, Mg-suite pluton. LROC NAC stereo images and Mini-RF data indicate the presence of several exposed pyroclastic fissures across the Sculptured Hills. Rim boulders at Camelot Crater constitute nearly in situ wall rocks of that crater rather than ejecta and provide an opportunity for investigations of remanent magnetic field orientation at the time of the eruption of late mare basalt lavas in the valley. Paleomagnetic field orientation information also may be obtained relative to melt-breccia contacts in North Massif boulders that suggest original horizontal orientations. LROC images indicate the existence of two temporally separate light mantle avalanche deposits. The origin, potential flow mechanisms, and geology of the youngest avalanche from the South Massif have been clarified. The existence of two distinct light mantle avalanches raises doubt about the association of either light mantle avalanche with secondary impacts related to the Tycho impact event. Alternatively, the Lee-Lincoln thrust fault appears to have triggered the second light mantle avalanche between 70 and 110 Ma. A simple structural analysis shows that this thrust fault dips 20–25° to the southwest where it crosses the North Massif and to the west where it crosses the valley floor. Mini-RF data reveal a line of reduced reflections roughly perpendicular to contours on the North Massif about 3 km to the east of the Lee-Lincoln fault. Although this line is possibly an older ancillary fault, LROC NAC stereo images indicate that it may be best explained as a pyroclastic fissure. A debris flow of dark, apparent pyroclastic ash lies below the southeast end of the potential fissure. Finally, young lunar impact glass sample 70019 has been precisely located within LROC NAC images and oriented for the first time using 60 mm (f.l.) sample documentation photographs. Sample 70019 can now be employed in lunar paleomagnetic field orientation studies.

Analysis of mineral compositions and crater morphology on the Moon surface using Moon orbital satellite data

Analysing vertical and lateral distribution of minerals within an impact crater on lunar surface would aid in understanding the crustal compositions to a larger extent and provides clue about geological evolution of the Moon. The Chandrayaan-1 Moon Mineralogy Mapper (M3) and Lunar Reconnaissance Orbiter Camera (LROC) data have high spectral and spatial resolutions, which help in identifying the mineral compositions and morphological features of impact crater. Here we analyse mineral compositions and their correlations with crater morphology using M3 and LROC satellite data of Eijkman impact cater in SouthPole Atiken (SPA) basin. The result shows that low-Ca pyroxene (LCP) dominant rocks are identified on Central Peak (CP), Crater Floor (CF), Crater Wall (CW) and Crater Rim (CR). An olivine dominant rock is detected on the CW. Fe-Mg-spinel lithological unit is observed on the CF. The results implicate that, (i) Low-Ca pyroxene minerals could be from the lower crust during SPA main event; (ii) Presence of olivine and Fe-Mg-spinel lithology on the surface could be a later stage mafic intrusions or the lower-crustal material exposed on the surface due to major impacts.

Detection of hydroxyl-bearing exposures of possible magmatic origin on the central peak of crater Theophilus using Chandrayaan-1 Moon Mineralogy Mapper (M3) data

High-resolution spectral and spatial data analyses of crater Theophilus revealed the presence of hydroxyl-bearing exposures of possible magmatic origin on its central peak in association with olivine-, spinel- and crystalline plagioclase-bearing lithologies. Hydroxyl-bearing lithologies at Theophilus central peak are characterized primarily by a prominent absorption feature near 2800nm, the strength of which varies from ∼2% to 6% in some localized zones within the central peak. The strong and sharp 2800-nm hydroxyl feature having localized occurrences on the central peak of crater Theophilus is inconsistent with a surficial origin. We suggest that the observed hydration at Theophilus central peak could possibly be associated with a sub-crustal magmatic source that was subsequently tapped and exposed by Theophilus impact event.

Lunar absolute reflectance as observed by Chang’E-1 Imaging Interferometer

Lunar absolute reflectance, which describes the fraction of solar radiation reflected by the Moon, is fundamental for the Chang’E-1 Imaging Interferometer (IIM) to map lunar mineralogical and elemental distributions. Recent observations made by the Spectral Irradiance Monitor (SIM) onboard the Solar Radiation and Climate Experiment (SORCE) spacecraft indicate that temporal variation in the solar radiation might have non-negligible influence on reflectance calculation, and the SIM measurements are different from the two previously used solar irradiances, i.e., ATLAS3 and Newkur. To provide reliable science results, we examined solar irradiance variability with the SIM daily observations, derived lunar absolute reflectances from the IIM 2A radiance with the SIM, ATLAS3 and Newkur data, and compared them with the Chandrayaan-1 Moon Mineralogy Mapper (M3), the Robotic Lunar Observatory (ROLO) and the Kaguya Multispectral Imager (MI) results. The temporal variability of the SIM solar irradiance is 0.25%–1.1% in the IIM spectral range, and less than 0.2% during the IIM observations. Nevertheless, the differences between the SIM measurements and the ATLAS3 and Newkur data can respectively rise up to 8% and 5% at particular IIM bands, resulting in discrepancy between which might affect compositional mapping. The IIM absolute reflectance we derived for the Moon using the SIM data, except for the last two bands, is consistent with the ROLO and the MI observations, although it is lower.

Multiple origins for olivine at Copernicus crater

Multiple origins for olivine-bearing lithologies at Copernicus crater are recognized based on integrated analysis of data from Chandrayaan-1 Moon Mineralogy Mapper (M3), Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) and Kaguya Terrain Camera (TC). We report the diverse morphological and spectral character of previously known olivine-bearing exposures as well as the new olivine occurrences identified in this study. Prominent albedo differences exist between olivine-bearing exposures in the central peaks and a northern wall unit (the latter being ∼40% darker). The low-albedo wall unit occurs as a linear mantling deposit and is interpreted to be of impact melt origin, in contrast with the largely unmodified nature of olivine-bearing peaks. Small and localized occurrences of olivine-bearing lithology have also been identified on the impact melt-rich floor, representing a third geologic setting (apart from crater wall and peaks). Recent remote sensing missions have identified olivine-bearing exposures around lunar basins (e.g. Yamamoto et al., 2010; Pieters et al., 2011; Kramer et al., 2013) and at other craters (e.g. Sun and Li, 2014), renewing strong interest in its origin and provenance. A direct mantle exposure has commonly been suggested in this regard. Our detailed observations of the morphological and spectral diversity in the olivine-bearing exposures at Copernicus have provided critical constraints on their origin and source regions, emphasizing multiple formation mechanisms. These findings directly impact the interpretation of olivine exposures elsewhere on the Moon. Olivine can occur in diverse environments including an impact melt origin, and therefore it is unlikely for all olivine exposures to be direct mantle occurrences as has generally been suggested.

Volcanism on farside of the Moon: New evidence from Antoniadi in South Pole Aitken basin

The lunar surface is characterized by asymmetric distribution of its volcanic deposits. The nearside contains about 90% of the mare basalts, while there are a few on the farside with some are in the South Pole Aitken (SPA) basin, which is the largest and oldest impact basin on the Moon. Although the mare volcanism on the nearside of the Moon has been very well characterized, our understanding of the farside is relatively poor. Our geological mapping using Lunar Reconnaissance Orbiter (LRO) and Chandrayaan-1 Moon Mineralogy Mapper (M3) data of 143km Antoniadi impact basin provides new insights into volcanic processes in the southern SPA. Antoniadi has excavated the SPA floor as deep as 9km. Distribution of secondary craters around Antoniadi shows that the basin was formed by oblique impact with the direction of 50° counter-clockwise from 178°E longitude. Our geological mapping has found, for the first time, several volcanic cones (0.2–2.5km diameter) in association with the mare basalt flows. As per morphological classification, these are C, E, N and P type volcanic cones with abundant volcanic fragments in their summit areas. The base and summit diameters of these cones are similar to those of Marius Hills on the nearside of the Moon. The cumulative size frequency distributions of the summit fragments provide a range of power index values between −3 and −9, suggesting the involvement of dynamic fragmentation of the volcanic materials during the eruptive processes. The grabens in the basin floor show evidence for fissure eruption of the mare basalts. The graben near the central peak exposes about 140m thick basalt sequence containing a minimum of five individual lava layers. The crater size–frequency distributions of the mare deposits suggest an age of 1.6Ga for the flows in the central part of the basin, while 2.6Ga for those on the outer floor near the basin wall, indicating the episodic volcanism in the basin. The young volcanism of 1.6Ga is reported for the first time from SPA. The M3 data reveal that the basin materials contain abundant low-Ca pyroxene, while the mare basalts with high-Ca pyroxene. We calculated the liquidus density of mare basalts based on FeO and TiO2 content, which suggest a range of density from 2.7 to 2.8g/cm3, which would be lower than a gross lunar crust. This would imply the emplacement of basaltic lavas through dikes by simple magma buoyancy or over-pressurization of magma chambers, if they present at the crust-mantle boundary when the magma density is greater than the host crust. The 1.6Ga old volcanism in Antoniadi suggests that the mantle beneath the SPA has been conducive for young magmatism, possibly due to presence of KREEP like material in the mantle.

Geological features and evolution history of Sinus Iridum, the Moon

The Sinus Iridum region is one of the important candidate landing areas for the future Chinese lunar robotic and human missions. Considering its flat topography, abundant geomorphic features and complex evolutionary history, this region shows great significance to both lunar science and landing exploration, including powered descent, surface trafficability and in-situ exploration. First, we use Lunar Reconnaissance Orbiter (LRO) Altimeter (LOLA) and Camera (LROC) data to characterize regional topographic and geomorphological features within Sinus Iridum, e.g., wrinkle ridges and sinuous rilles. Then, we deduce the iron and titanium content for the mare surface using the Clementine ultraviolet–visible (UVVIS) data and generate mineral absorption features using the Chandrayaan-1 Moon Mineralogy Mapper (M3) spectrometer data. Later, we date the mare surface using crater size-frequency distribution (CSFD) method. CSFD measurements show that this region has experienced four major lava infilling events with model ages ranging from 3.32Ga to 2.50Ga. The regional magmatic activities evolved from Imbrian-aged low-titanium to Eratosthenian-aged medium-titanium. The inner Sinus Iridum is mainly composed of pyroxene-rich basalts with olivine abundance increasing with time, while the surrounding highlands have a feldspar-dominated composition. In the northern wall of Sinus Iridum, some potential olivine-rich materials directly excavated from the lunar mantle are visible. The Sinus Iridum region is an ideal target for future landing exploration, we propose two candidate landing sites for the future Chinese robotic and human missions.

Near-infrared spectra of ferrous mineral mixtures and methods for their identification in planetary surface spectra

Iron-bearing minerals are a major component of planetary surfaces, and many can be identified by their characteristic absorption bands in the near-infrared (NIR). Here we present laboratory NIR spectra of a wide range of common Fe-bearing minerals (e.g., olivines, pyroxenes), glasses, and mineral/glass mixtures. We then use this suite of spectra to evaluate the effects of mixtures on mineral detection methods, including olivine and pyroxene spectral indices developed for the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard Mars Reconnaissance Orbiter. We find that although these indices can be compromised by minerals with atypical compositions, mineral mixtures, and the presence of other ferrous minerals, these issues can generally be mitigated by visual inspection of the spectra. However, a special case occurs when the mineral or mixture in question is spectrally indistinguishable from a more common mineral. In particular, we show that spectra of high-calcium pyroxene mixed with Fe-bearing glass can be virtually indistinguishable from common Fe-bearing olivine compositions. This effect, combined with the fact that Fe-bearing glass is generally much more difficult to detect than other ferrous minerals, may be causing glass occurrences on planetary surfaces to be underreported. In support of this hypothesis, we use Mars Express OMEGA observations to show that previous olivine detections in the north polar sand sea on Mars are actually more consistent with local mixing of glass and pyroxene. To address these issues, we present an alternative ferrous mineral identification method based on the position and shape of the 1 and 2μm iron absorption bands, which are sensitive to mineralogy, composition, and mineral mixtures in planetary surface spectra, including glass and mixtures with glass. Using Chandrayaan-1 Moon Mineralogy Mapper (M3) observations of Aristarchus Crater on the Moon, we show that these band parameters can reveal subtle spectral variations and can produce mineralogical maps at an exceptional level of detail.

Compositional diversity of near-, far-side transitory zone around Naonobu, Webb and Sinus Successus craters: Inferences from Chandrayaan-1 Moon Mineralogy Mapper (M3) data

This study investigated the potential of Moon Mineralogy Mapper (M3) data for studying compositional variation in the near-, far-side transition zone of the lunar surface. For this purpose, the radiance values of the M3 data were corrected for illumination and emission related effects and converted to apparent reflectance. Dimensionality of the calibrated reflectance image cube was reduced using Independent Component Analysis (ICA) and endmembers were extracted by using Pixel Purity Index (PPI) algorithm. The selected endmembers were linearly unmixed and resolved for mineralogy using United States Geological Survey (USGS) library spectra of minerals. These mineralogically resolved endmembers were used to map the compositional variability within, and outside craters using Spectral Angle Mapper (SAM) algorithm. Cross validation for certain litho types was attempted using band ratios like Optical Maturity (OMAT), Color Ratio Composite and Integrated Band Depth ratio (IBD). The identified lithologies for highland and basin areas match well with published works and strongly support depth related magmatic differentiation. Prevalence of pigeonite-basalt, pigeonite-norite and pyroxenite in crater peaks and floors are unique to the investigated area and are attributed to local, lateral compositional variability in magma composition due to pressure, temperature, and rate of cooling.