Icarus 222 (2013) 137–148

Contents lists available at SciVerse ScienceDirect

Icarus

journal homepage: www.elsevier .com/locate / icarus

Mineralogy of Mare Serenitatis on the near side of the Moon basedon Chandrayaan-1 Moon Mineralogy Mapper (M3) observations

Prabhjot Kaur, Satadru Bhattacharya ⇑, Prakash Chauhan, Ajai, A.S. Kiran KumarSpace Applications Centre (ISRO), Ahmedabad 380 015, India

a r t i c l e i n f o

Article history:Received 3 November 2011Revised 28 August 2012Accepted 10 October 2012Available online 6 November 2012

Keywords:MoonMineralogySpectroscopyVolcanism

0019-1035/$ - see front matter � 2012 Elsevier Inc. Ahttp://dx.doi.org/10.1016/j.icarus.2012.10.020

⇑ Corresponding author. Address: PMD/MPSG/EPSA(ISRO), Ambawadi Vistar P.O., Ahmedabad 380 015, In

E-mail address: satadru@sac.isro.gov.in (S. Bhattac

a b s t r a c t

Spectral analysis of Mare Serenitatis has been carried out using Chandrayaan-1 Moon Mineralogy Mapper(M3) data in order to map the compositional diversity of the basaltic units that exist in the basin. MareSerenitatis is characterized by multiple basaltic flows of different ages indicating a prolonged volcanismsubsequent to the basin formation event. Reflectance spectra of fresh craters from the Mare Serenitatishave been analyzed to study the nature and location of the spectral absorption features around 1- and2-lm respectively, arising due to the electronic charge transition of Fe2+ in the crystal lattice of pyroxenesand/or olivine. Chandrayaan-1 M3 data have been utilized to obtain an Integrated Band Depth (IBD)mosaic of the Serenitatis basin. Based on the spectral variations observed in the IBD mosaic, 13 spectralunits have been mapped in the Mare Serenitatis. In the present study, we have also derived spectral bandparameters, namely, band center, band strength, band area and band area ratio from the M3 data to studythe mineralogical and compositional variations amongst the basaltic units of the studied basin. On thebasis of spectral band parameter analysis, the pyroxene compositions of the basaltic units have beendetermined, which vary from low to intermediate end of the high-Ca pyroxene and probably representa sub-calcic to calcic augite compositional range. Detailed spectral analyses reveal little variations inthe mafic mineralogy of the mare basalts in terms of pyroxene chemistry. The uniformity in pyroxenecomposition across the basaltic units of Mare Serenitatis, therefore, suggest a probably stable basalticsource region, which might not have experienced large-scale fractionation during the prolonged volca-nism that resulted in filling of the large Serenitatis basin.

� 2012 Elsevier Inc. All rights reserved.

1. Introduction

Basaltic lava flows on the Moon account for about 17% of the lu-nar surface and occupy about 1% of the total volume of the lunarcrust (Head, 1976). The distribution, diversity and volume of themare basalts provide a record of the thermal evolution of the Moon(Taylor, 1989; Head and Wilson, 1992). Mare basalts on the lunarsurface have been mapped in terms of stratigraphy, compositionand evolution using a variety of techniques, for example photogeo-logic mapping, Spectroscopic studies (e.g., Visible/Near-Infrared,Gamma-Ray, X-ray Spectroscopy), etc. Earth-based telescopicobservations at low resolution (McCord et al., 1976; Pieters andMcCord, 1976; Pieters, 1977, 1978) and space-based high resolu-tion (Tompkins and Pieters, 1999; Bussey and Spudis, 2000; Pietersand Staid, 2000; Pieters et al., 2001; Staid and Pieters, 2001; Gigu-ere et al., 2003, 2006; Shkuratov et al., 2003; Ohtake et al., 2009;Klima et al., 2011; Staid et al., 2011) reflectance measurementsof the lunar surface in the Visible/Near-Infrared (VNIR) region have

ll rights reserved.

, Space Applications Centredia.

harya).

greatly expanded the knowledge about the distribution, diversity,mineralogy and compositional history of the Moon.

Mare basalts on the lunar surface encompass a wide range ofbasaltic compositions manifested in terms of variations in thespectral properties. The spatial and stratigraphic distribution ofthese spectrally distinct mare basalt entities hints towards thecompositional heterogeneity of the source region i.e. the lunarupper mantle, and suggests independent evolution of mare basins(Pieters, 1978). Various models have been developed for mare ba-salt generation, chemical characteristics and depth of a single,primitive source region by variable degrees of partial melting (Tay-lor and Jâkes, 1974; Papike et al., 1976; Ringwood and Kesson,1976; BVSP, 1981; Hess and Paramentier, 1995). Mare basalt min-eralogy, therefore, provides clue to the source region chemistry.

In view of the above, mare basalts have been studied andmapped extensively by the previous researchers. Mare units ex-posed on the eastern near side of the Moon are comparatively olderthan its western near side counterpart and mostly fall within the agerange of �4.0–3.0 Ga (i.e. the Imbrian and Nectarian periods) (Sod-erblom et al., 1977; Hiesinger et al., 2000). Not much volcanic activ-ity had taken place in the eastern near side since the Imbrian periodexcept for a few basaltic units that fall within the Eratosthenian

138 P. Kaur et al. / Icarus 222 (2013) 137–148

period. Previous works on the stratigraphy, composition and evolu-tion of near side mare basalts were carried out mainly based on theanalysis of telescopic data, Galileo Solid State Imager data, Clemen-tine data, and Lunar Prospector data (Pieters and McCord, 1976;Pieters, 1978; Belton et al., 1992; Lawrence et al., 1998).

Recent missions (Smart-1, Kaguya/SELENE, Chang’e-1, Chan-drayaan-1 and LRO) equipped with advanced very high spectraland spatial resolution instruments are providing unprecedenteddetails of the Moon necessary for better understanding of the lunarevolutionary history (Matsunaga et al., 2008; Morota et al., 2008;Goswami and Annadurai, 2009; Pieters et al., 2009; Besse et al.,2011; Isaacson et al., 2011; Klima et al., 2011; Staid et al., 2011).In the present study, reflectance data acquired by Chandrayaan-1M3 instrument have been used to map the mineralogical and com-positional variability of the basaltic units across Mare Serenitatis.

2. Background

2.1. Geology of Mare Serenitatis

Mare Serenitatis (26�N, 18�E), a 740-km diameter basin (Wil-helms, 1987), is one of the most prominent basalt-filled basinson the eastern near side of the Moon. At the eastern flank of MareSerenitatis, the basin-rim is obliterated by a 60-km diameter im-pact crater named Le Monnier (25�510N, 30�270E), which forms alarge bay by connecting itself to the main basin. A dark mantlematerial (DMM) deposit is also exposed at the southwest andsoutheast margins of the Serenitatis basin (Pieters, 1978). Fig. 1shows the mosaic of Mare Serenitatis generated using 1578-nmM3 channel, which is considered to be the lunar albedo.

Previous researchers delineated and classified the differentmare units of the Serenitatis basin primarily on the basis of ironand titanium content and also estimated the absolute model agesbased on crater-size frequency distribution (CSFD) technique (Piet-ers and McCord, 1976; Pieters, 1978; Johnson et al., 1991; Headand Wilson, 1992; Lucey et al., 1998; Hiesinger et al., 2000; Staidand Pieters, 2001; Kodama and Yamaguchi, 2003; Hackwill,2010). Pieters (1978) classified Mare Serenitatis into five groupsas HDWA, hDWA, mISP, LIG and a dark mantle material (DMM)on the basis of UV/VIS slope, Albedo, 1-lm band strength and pres-ence of 2-lm absorption as obtained from Earth-based telescopicobservations and orbit-based multispectral data. The majority ofthe basalts exposed at the central part of Mare Serenitatis weredesignated as mISP by Pieters (1978). Hiesinger et al. (2010) iden-tified and dated 29 spectral units ranging in age from 3.81 to2.44 Ga suggesting that the volcanism in the Serenitatis basinwas active over a protracted period of �1.4 Ga. Almost 33% basalticunits were formed in a time spam of around 200 Ma between 3.8and 3.6 Ga with an additional 23% basalts were emplaced between3.5 and 3.4 Ga. On the basis of spectral analysis of Clementine UV/VIS multispectral data and Clementine-derived data including FeOand TiO2 wt% maps, Kodama and Yamaguchi (2003) have identifiedsix groups in Mare Serenitatis. The basalts exposed in the centralpart of Mare Serenitatis have been characterized as low-Ti (2.8–4.2 wt%) basalts (Kodama and Yamaguchi, 2003). The FeO wt%map obtained from LP-GRS data showed that the central basaltshave high FeO content whereas the surrounding basalts have beencharacterized by low FeO content (Lawrence et al., 2002). Recentwork on Mare Serenitatis includes identification and mapping of14 distinct basaltic units on the basis of differences in TiO2 wt%and age (Hackwill, 2010). According to Hackwill (2010), however,no apparent trend was observed in terms of variations in FeOand TiO2 wt% with time in these basaltic units.

In the present study, a quantitative approach has been adoptedto further refine the existing knowledge of the basalt composition

in Mare Serenitatis based on the analysis of hyperspectral data ac-quired by Chandrayaan-1 M3 instrument.

2.2. Spectroscopy of lunar minerals

Among the mafic lunar minerals, pyroxenes and olivine are themost abundant and are easily recognizable due to their diagnosticspectral absorption features around 1 and 2 lm (Adams, 1974,1975; Burns, 1970; Cloutis, 1985). The primary diagnostic featurein olivine is a composite of three distinct absorption bands near1-lm, which is attributed to the electronic transitions of Fe2+ occu-pying both the M1 and M2 crystallographic sites (Burns, 1970,1974, 1993; King and Ridley, 1987; Sunshine and Pieters, 1998;Sunshine et al., 2000).

Pyroxenes, the single-chain silicates, crystallize either in ortho-rhombic or monoclinic symmetry groups (Morimoto et al., 1988).Both monoclinic and orthorhombic pyroxenes have two octahedralsites, M1 and M2, where M2 site is much larger and distorted ascompared to M1. The partitioning of Fe2+ cations in M1 and M2sites is highly dependent on bulk composition of pyroxene, tem-perature and pressure of formation, cooling rate, etc. (e.g., Saxenaand Ghose, 1971). In the near-infrared spectral domain, pyroxenesshow two major absorption features near 1 and 2 lm, which oc-curs due to electronic transitions of Fe2+ present in the asymmetricM2 site (Clark, 1957; Adams, 1974; Burns, 1993; Cloutis et al.,1986; Cloutis and Gaffey, 1991a). However, Fe2+ ion in more sym-metric M1 site produces much weaker absorption features at 1 and1.2 lm (Klima et al., 2008, 2010) respectively. The 1.2-lm absorp-tion feature is prominent in high-Fe ortho- and clinopyroxenes, thearea and strength of which reflects the cooling history of a pyrox-ene bearing planetary body (Klima et al., 2008). Presence of Fe2+ inminute quantities in the crystal lattice of plagioclase also gives riseto absorption feature around 1.2 lm (Burns, 1993) which can beeasily confused with the M1 absorption of Fe-rich low- and high-Ca pyroxenes and/or olivine. In low-Ca pyroxenes, i.e., orthopyrox-enes, the 1-lm absorption feature (Band I) ranges from 0.90 to0.93 lm, whereas the 2-lm (Band II) band center varies from1.80 to 2.10 lm (Cloutis and Gaffey, 1991b). The Band I and BandII absorptions in Type B high-Ca pyroxenes vary from 0.91 to1.07 lm and 1.97–2.36 lm respectively (Cloutis and Gaffey,1991b), as smaller Mg2+ ions in M2 site are replaced by largerCa2+ and Fe2+ ions (Adams, 1974; Hazen et al., 1978; Burns,1993; Cloutis and Gaffey, 1991b).

In case of mineral mixtures, the 1-lm region is highly influ-enced by the overlapping absorptions from low- and high-Capyroxenes, olivine and Fe-bearing crystalline plagioclase, thusmaking the interpretations difficult. For olivine–orthopyroxenemixtures, the Band II is sensitive to the pyroxene abundance, whileBand I is dependent on relative abundances and compositions ofboth olivine and pyroxene phases (Cloutis et al., 1986). The relativearea of Band I and Band II absorption features (Band II/Band I arearatio, i.e., BAR) is a useful quantity for estimating the relative abun-dances of pyroxene and olivine (Cloutis et al., 1986). The BAR valueis higher for pyroxene dominated lithologies and decrease with in-crease in the olivine content. In the absence of any 2-lm absorp-tion feature in pure olivine spectra, the BAR value of pure olivinephase becomes zero (Cloutis et al., 1986). Gaffey et al. (1993) de-fined three silicate compositional groups, namely, OL, OC and BAto denote monomineralic olivine assemblages, mafic silicate com-ponents of ordinary chondrites and pyroxene-dominated basalticachodrite assemblages respectively on the basis of the Band I cen-ter versus the Band II/Band I area ratio (BAR) plot.

Moon being an airless body is constantly assailed by the microme-teorites and high-energy particles. This continuous exposure of thelunar surface results in the formation of complex agglutinitic glassesand vapor-deposited grain coatings containing sub-microscopic

P. Kaur et al. / Icarus 222 (2013) 137–148 139

nanophase reduced iron (Hapke, 1975, 2001; Basu, 1977, 2005; Tayloret al., 2001). Space weathering results in the lowering of albedo,weakening of the absorption band depths, and in many cases,reddening of spectral slope of the lunar minerals. The diagnosticabsorptions may be substantially weakened by these effects, but theyare not completely eliminated (Pieters et al., 2000; Hapke, 2001;Noble et al., 2007). The deposition of vapor-deposited nanophase ironon the rims of the lunar grains predominantly increase the continuumslope of near-IR spectra of lunar surface materials (e.g., Hapke, 2001;Pieters et al., 2000; Taylor et al., 2001, 2010). On the contrary, rela-tively unweathered materials associated with young impact craterspreserve diagnostic absorption features that are indicative of miner-alogy of the remote planetary surface (e.g., Pieters, 1977; McCordet al., 1981). These optically immature materials exposed by theyoung impact craters are of prime importance and thus provideopportunity to study the surface mineralogy without the addedcomplication of space-weathering-induced changes to the opticalproperties of the lunar materials.

3. Instrument and data used

M3 was a guest instrument onboard Chandrayaan-1, ISRO’s mai-den mission to the Moon (Goswami and Annadurai, 2009). M3 col-lected data in five different optical periods (OPs): OP1A, OP1B,OP2A, OP2B and OP2C (Boardman et al., 2011; Green et al.,2011). The spacecraft obtained data at a spatial resolution of�140 m/pixel from 100-km orbit and 280 m/pixel when the orbitwas raised to 200 km (Boardman et al., 2011). The detailed descrip-tion of the calibration of M3 data is provided by Green et al. (2011),and a description of the operational history and spatial coverage ofM3 is provided by Boardman et al. (2011). The Level 2 (L2) productincludes photometrically calibrated, pixel-located reflectance datawhich is also corrected for thermal emissions. The L2 reflectancedata, acquired during optical period OP2C, have been used in thisstudy. The mosaic presented in Fig. 1 has been generated using1578-nm albedo channel. The albedo mosaic of Mare Serenitatis

Fig. 1. M3 albedo mosaic (1578-nm

consists of 12 individual M3 image strips; the gap in the mosaicrepresents lack of data coverage during the OP2C acquisition peri-od (Fig. 1). The operation of detector above its nominal tempera-ture leads to degradation of the signal-to-noise ratio andcontributes to the vertical stripping (Green et al., 2011) in theimages as evident from Figs. 1 and 2.

4. Methods

4.1. Integrated Band Depth (IBD) analysis

In this study, Integrated Band Depth (IBD) mosaic has been gen-erated to depict the spectral variability amongst the basaltic unitsof Mare Serenitatis. A summary of information for the image prod-uct ID, date of acquisition, and phase angle is given in Table 1. Theaccurate assessment of absorption band strength of the lunarmaterials requires removal of the continuum slope imparted bythe space weathering process (e.g., Clark and Roush, 1984). Contin-uum removal has been performed by using convex hull method gi-ven by Clark and Roush (1984). Subsequent to continuum removal,the local mafic mineral band strength is calculated by an IntegratedBand Depth parameter (IBD) developed by M3 team (e.g., Mustardet al., 2011).

The IBD parameter is defined for characterizing the band depthsfor 1- and 2-lm absorption features in order to capture the spec-tral variations related to mafic minerals, soil maturity, and spaceweathering (Mustard et al., 2011). Thermal emission in the lunarspectrum begins after 2 lm, causing the upturn of the spectrumtail towards higher wavelengths. Clark et al. (2011) explained theremoval of the thermal emission from the M3 spectrum which isimportant for interpreting the mineralogical details based on BandII absorption feature. In order to get rid of the thermal perturbationin the reflectance data as observed in the previous M3 Level 1b dataproducts, we have used M3 L2 thermally corrected reflectance datafor the present purpose to precisely characterize the 2-lm (BandII) absorption feature. The IBD for 1- and 2-lm absorption features

channel) of Mare Serenitatis.

Fig. 2. IBD mosaic of Mare Serenitatis as obtained using M3 L2 global datasets. The mare basalts appear yellow to yellowish green in the IBD mosaic due to the absorption near1 and 2 lm and are easily distinguishable from highlands, which appear blue in the IBD mosaic due to the lack of mafic absorption features. Black solid line demarcates theboundaries of the spectral units mapped in the present study. Circles marked in the IBD parameter image represent the craters having a 1.2-lm absorption feature. (Forinterpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Table 1Details of M3 data used for studying Mare Serenitatis.

Sr. no. Data strip file name Date Phase angle (�) Orbit altitude (km)

1 M3G20090607T025544_V01_RFL 7-June-09 31.5 2002 M3G20090606T053022_V01_RFL 6-June-09 19.02 2003 M3G20090607T070124_V01_RFL 7-June-09 23.2 2004 M3G20090607T110414_V01_RFL 7-June-09 27.3 2005 M3g20090607t201038_V01_RFL 7-June-09 30.3 2006 M3g20090608t000122_V01_RFL 8-June-09 32.3 2007 M3g20090608t042049_V01_RFL 8-June-09 33.4 2008 M3g20090730t205153_V01_RFL 30-July-09 45.5 2009 M3g20090731t005012_V01_RFL 31-July-09 40.9 200

10 M3g20090731t045352_V01_RFL 31-July-09 46.2 20011 M3g20090731t092152_V01_RFL 31-July-09 47.1 20012 M3g20090607t153144_V01_RFL 7-June-09 28.02 200

140 P. Kaur et al. / Icarus 222 (2013) 137–148

is defined as the total integrated band depth calculated using equa-tions given by Mustard et al. (2011). The 1578-nm wavelength re-gion is free from any lunar mafic silicate absorption, therefore, theIBD parameter mosaic of 1- and 2-lm band depths together withalbedo band at 1578-nm captures the first-order mineralogicalvariations. False Color Composites (FCCs) have been prepared byassigning Red color to IBD-1, Green to IBD-2 and Blue to the1578-nm albedo channel. We have used this color composite tocharacterize spectral diversity across the Serenitatis basin, whichrepresents the net effect of composition, maturity and contamina-tion by the highland materials.

4.2. Spectral analysis

To characterize the reflectance properties of the spectral unitsidentified in the M3 IBD mosaic of Mare Serenitatis, spectral band

parameters have been computed for each of the individual spectralunits. A large number of fresh craters were sampled from each unitin order to capture the spectral variability of each of the individualunits (Appendices A and B). It is crucial to take immature spectrafrom fresh craters to avoid unwanted effects of space weatheringrelated optical maturity which causes apparent shifts in the bandcenter positions (e.g., Clark and Roush, 1984; Clark, 1999). Wehave, therefore, chosen craters that are large enough to excavatethe immature fresh materials from underneath. Craters having adiameter of <�1 km have been sampled from each of the individualspectral units. Mean spectra were calculated from maximum of 5–6 pixels (the no. of pixels vary according to the size of the craters)from individual fresh craters. To compare the relative maturity ofthe units, scatter plot of 1-lm band strength (defined as the ratioof 950- to 750-nm reflectance) versus 750-nm reflectance has beengenerated for each of the mapped spectral units. The mean

0.02

0.06

0.1

0.14

0.18

500 1000 1500 2000 2500

Ref

lect

ance

Wavelength (nm)

500 1000 1500 2000 2500Wavelength (nm)

500 1000 1500 2000 2500Wavelength (nm)

500 1000 1500 2000 2500Wavelength (nm)

500 1000 1500 2000 2500Wavelength (nm)

500 1000 1500 2000 2500Wavelength (nm)

500 1000 1500 2000 2500Wavelength (nm)

500 1000 1500 2000 2500Wavelength (nm)

500 1000 1500 2000 2500Wavelength (nm)

Unit S1Unit S2Unit S3Unit S6Unit S8

0.6

0.7

0.8

0.9

1

0.02

0.06

0.1

0.14

0.18

0.22

(i) (iii)(ii)

0.6

0.7

0.8

0.9

1

0.02

0.06

0.1

0.14

0.18

0.02

0.06

0.1

0.14

0.18

Ref

lect

ance

Unit S4

Unit S5

Unit S7

(vii) (ix)(viii)

0.6

0.7

0.8

0.9

1

0.02

0.06

0.1

0.14

0.18

0.04

0.08

0.12

0.16

Ref

lect

ance

Unit S9Unit S10Unit S11Unit S12Unit S13

(iv) (vi)(v)

(a)

Fig. 3. (a) Mean normal (without and with vertical offset) and continuum-removed reflectance spectra of fresh craters as sampled from (i–iii) western and central units (S1,S2, S3, S6 and S8), (iv–vi) eastern units (S9, S10, S11, S12 and S13) and (vii–ix) southwestern and southern units (S4, S5 and S7) near the mare-highland boundary; (b)reflectance spectra of matured soil (A) without vertical offset and (B) with vertical offset from (i) western and central (S1, S2, S3, S6 and S8), (ii) southwestern and southern(S4, S5 and S7) and (iii) eastern (S9, S10, S11, S12 and S13) units of Mare Serenitatis.

P. Kaur et al. / Icarus 222 (2013) 137–148 141

reflectance spectra of the most matured pixels are taken from thedensest part of the data cloud (e.g., Isaacson and Pieters, 2009). Thedetails of the spectral units, latitude, and longitude of the craterssampled and the band parameters computed are presented inAppendix A.

We performed the band parameter analysis to derive the cen-tral wavelengths of the 1- and 2-lm pyroxene–olivine absorptionfeatures designated as Bands I and II respectively and the ratio ofBand II to Band I area known as Band Area Ratio (BAR) (Cloutiset al., 1986; Gaffey et al., 2002) (Appendix A). In order to computethe band center, band strength and band area values precisely, wehave performed continuum removal by fitting a straight line con-tinuum tangent on both side of the absorption band for the BandsI and II separately and dividing the spectra by the respective con-tinuum. The points of ‘‘highest reflectance’’ on either side of theabsorption minimum have been considered to be the tangentpoints. For band I, the short-wavelength inflection point typically

falls between 750 and 770 nm whereas the long-wavelengthinflection point falls between 1600 and 1700 nm. Band II is consid-ered up to 3.0 lm as the data is corrected for thermal emissioncomponent. Band center is calculated by fitting a 3rd order polyno-mial to the bottom of the continuum-removed absorption featureand the minimum point on the polynomial fit is considered asthe band center. The errors associated with the band center com-putation have been determined through an iterative processwhereby the number of points on either side of the visually deter-mined band minima are changed three to four times and band cen-ter values are computed each time. The average error associatedwith the band center estimation is found to be ±0.01 lm. Band areais calculated as the area between the continuum slopes and thedata points. The spectral band parameters, thus computed, allowquantification of the surface mineralogy, relative mafic mineralabundances (olivine/ortho- and/or clinopyroxene) and pyroxenechemistry.

(i)0.02

0.06

0.1

0.14

0.18

500 1000 1500 2000 2500

Ref

lect

ance

Wavelength (nm)

Unit S1Unit S2Unit S3Unit S6Unit S8

(ii)0.02

0.06

0.1

0.14

0.18

500 1000 1500 2000 2500

Ref

lect

ance

Wavelength (nm)

Unit S4

Unit S5

Unit S7

(iii)0.02

0.06

0.1

0.14

0.18

500 1000 1500 2000 2500

Ref

lect

ance

Wavelength (nm)

Unit S9

Unit S10

Unit S11

Unit S12

Unit S13

A

0.03

0.07

0.11

0.15

0.19

500 1000 1500 2000 2500

Ref

lect

ance

Wavelength (nm)

Unit S1Unit S2Unit S3Unit S6Unit S8

(i)

0.02

0.06

0.1

0.14

0.18

500 1000 1500 2000 2500

Ref

lect

ance

Wavelength (nm)

Unit S4

Unit S5

Unit S7

(ii)

0.02

0.06

0.1

0.14

0.18

500 1000 1500 2000 2500

Ref

lect

ance

Wavelength (nm)

Unit S9Unit S10Unit S11Unit S12Unit S13

(iii)

B(b)

Fig. 3. (continued)

Table 2Details of the mean spectra as obtained from the fresh craters of each of the 13spectral units across Mare Serenitatis.

Unitname

Reflectance at1578 nm

Band I strength(%)

Band II strength(%)

S1 0.13 23.03 18.55S2 0.12 20.25 16.10S3 0.12 22.75 16.61S4 0.12 22.11 15.43S5 0.12 22.11 17.89S6 0.13 24.41 19.46S7 0.14 12.30 11.41S8 0.13 24.50 19.70S9 0.13 28.14 21.04S10 0.12 28.14 23.69S11 0.11 26.69 23.12S12 0.10 22.23 18.51S13 0.11 9.43 9.44

142 P. Kaur et al. / Icarus 222 (2013) 137–148

The relationship between the spectral band parameters as ob-tained from the reflectance spectra and the chemistry of the maficminerals, namely, pyroxenes and olivine were well studied anddocumented by previous researchers (Adams, 1974, 1975; Kingand Ridley, 1987; Cloutis and Gaffey, 1991a). These relationshipswere used to formulate calibration equations for remote composi-tional assessment of pyroxenes by Gaffey et al. (2002). They used awide variety of pyroxenes, primarily terrestrial, at room tempera-ture for estimating the pyroxene chemistry vis-à-vis spectralparameters and finally came up with a set of calibration equations.These equations work well for single pyroxene or a low amount ofsecond pyroxene and more error is introduced when a secondpyroxene phase is present. In the present study, we have usedequations proposed by Gaffey et al. (2002) for estimating theEnstatite (En), Ferrosilite (Fs) and Wollastonite (Wo) content ofthe Serenitatis pyroxenes.

1.04

1.06

1.08

DL-CMP-054-Wo23En6Fs70

P. Kaur et al. / Icarus 222 (2013) 137–148 143

5. Results

5.1. IBD mosaic and spectral units

The IBD mosaic of Mare Serenitatis generated using M3 L2 datais shown in Fig. 2. Thirteen spectral units have been identified andmapped on the basis of spectral variations as observed in the IBDmosaic. The spectral units are divided into three categories basedon their locations, namely, western and central group consistingof units S1, S2, S3, S6 and S8; eastern group consisting of S9, S10,S11, S12 and S13 units; southwestern and southern group consist-ing of units S4, S5 and S7 (Fig. 2). Basalts of Mare Serenitatis dis-play yellow to yellowish green hue in the IBD mosaic, whereasthe highland region surrounding the mare appears blue in the colorcomposite. The localized variations in the mafic band strength areobserved in fresh craters (bright yellow to light pink in the colorcomposite). The black boundaries in Fig. 2 demarcate the extentof the various spectral units mapped within the Serenitatis basin.Eastern basaltic units display relatively greater variations as com-pared to western units probably due to the residual cross-trackproblems in the photometric correction and therefore, may notbe related to compositional/maturity differences.

The units mapped in the earlier studies based on TiO2 and FeOwt% and absolute model ages are not similar (Hiesinger et al.,2003; Hackwill, 2010; Kodama and Yamaguchi, 2003; Pieters,1978) to the spectral units mapped in the present study on the ba-sis of IBD variations. Nevertheless, the absolute model ages ob-tained on the basis of CSFD analysis by Hiesinger et al. (2000)can be considered for broadly defining the ages of the spectralunits identified in the present study. Mare units S1, S2 and S4, ex-posed on the western side, appear yellow to yellowish green in theIBD mosaic and range in age from 3.43 to 2.90 Ga, whereas, thecentral part of the mare basin, consisting of units S3, S6 and S8,vary in age from�3.49 to 2.84 Ga. The units encompassing the cen-tral part of the basin also show tonal variations in the IBD mosaicfrom yellow to orange to purple. The craters of these units appearmuch brighter (yellow to orange in color) as compared to the otherunits. Units S5 and S7 (age �3.76–3.71 Ga) represent oldest unitsdemarcating the mare highland boundary and appear bright yel-low to yellowish green in the color composite. The fresh cratersof these units appear blue in IBD mosaic. The eastern mare unitsS9 and S10 (age �3.44 and 2.84 Ga) appear blue to bluish greento purple in the IBD mosaic. The northern and southern parts ofunit S11 appear bluish green, whereas central part appears yellowto orange. Crater Le Monnier, a �60-km diameter crater along theeastern flank of Mare Serenitatis, represents unit S12, which is alsothe youngest unit having an age of �2.44 Ga (Hiesinger et al., 2000,2003). This unit appears yellowish orange in the IBD mosaic.

0.88

0.90

0.92

0.94

0.96

0.98

1.00

1.02

1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6

Ban

d I C

ente

r

Band II Center

OPX_ Adams Ca - PX_ Adamsopx_klimacpx_klimaMare Serenitatis

DL-CMP-038-Wo9En91c

DL-CMP-014-Wo3En39Fs59

Fig. 4. Band center data plotted on Band I versus Band II plot of Adams (1974), asmodified by Cloutis and Gaffey (1991a). Synthetic pyroxene data from Klima et al.(2011) is also plotted for comparison. Band center values of the fresh craters ofMare Serenitatis fall in the low- to moderate-Ca pyroxene domain indicating sub-calcic to calcic augite compositional range.

5.2. Analysis of reflectance spectra

Spectra of the fresh craters from most of the basaltic units ofMare Serenitatis display strong 1- and 2-lm absorption featureswith subtle variations in band strength, band center and band area.Fig. 3a represents the normal (without and with vertical offset forclarity) and continuum-removed mean of the reflectance spectrafrom the fresh craters sampled from each of the 13 spectral units.Details of the mean spectra in terms of mean Bands I and IIstrengths and mean albedo are given in Table 2. Spectra, fromwhich the mean and the spectral band parameters of each of thespectral units have been computed, are shown in Appendix B andthe band parameters are presented in Appendix A. The mean spec-tra of all the units of Mare Serenitatis (Fig. 2) are characterized by arelatively stronger Band I strength as compared to the Band IIstrength (except for the units S7 situated at the southern

mare-highland boundary and S13 along the southeastern cornerof the basin) (Fig. 3a). Also, it is evident from Fig. 3a that the meanband strengths of the eastern Mare Serenitatis units are relativelystronger than that of the western units with the sole exception ofunit 13, which is having the weakest band strengths of all. Overall,unit 13 is characterized by very weak and subdued 1- and 2-lmfeatures having relatively stronger 2-lm band strength, whichcould be attributed to the presence of spinel as a mixture in smallquantities. Spectra from the fresh craters of unit S13 having veryweak to non-existent absorption features around 1 and 2 lm prob-ably represent basin-derived impact melt or melt breccias (Fig. 3aand Appendix B).

The mean Band I strength of the spectral units of Mare Sereni-tatis varies from �20% in case of unit S2 to �28% in units S9 andS10 (Fig. 3a), whereas, Band II strength ranges from �16% in S2to �24% in S10 (Fig. 3a). The average albedo (based on the meanspectra from fresh craters) of the spectral units are found to varyfrom a maximum of �14% in unit S7 to a minimum of �10% as seenin unit S12 (Fig. 3a). The average albedo of matured soil from wes-tern, central and south-central part of Mare Serenitatis (covered byunits S1, S2, S3, S6 and S8) is found to be�9% (Fig. 3b). Unit S12 i.e.,crater Le Monnier represents the youngest unit of the Serenitatisbasin and hosts fresh craters that are characterized by the lowestmean albedo of �10% amongst all the units. On the contrary, themean matured soil albedo of S12 unit is the highest (�10%)amongst all the spectral units belonging to the eastern part of MareSerenitatis. It has been observed from the spectral analysis that themean mature-soil albedo of whole of the eastern Mare Serenitatisis lower (�7%) than that of its western counterpart (Fig. 3b). Themature soil spectra from unit S13 completely lack 1- and 2-lmabsorption features that are otherwise present in the matured soilspectra of rest of the units (Fig. 3b) and also the average albedo ofmatured soil from S13 unit records the minimum value of �5%(Fig. 3b). Spectral units S4, S5 and S7 share the mare-highlandboundary all along the southwestern and southern part of MareSerenitatis (Fig. 2). The average albedo of the fresh craters fromthe units S4 and S5 is found to be �12% and fresh craters of boththe units are characterized by prominent 1- and 2-lm absorptionfeatures. However, the fresh craters of unit S7 are characterizedby relatively subdued absorption features with an average albedoof �14%, which is also the highest amongst all the units (Fig. 3aand Appendix B). The average matured-soil albedo of spectral unitsS4, S5 and S7 are observed to be �9% (Fig. 3b).

Unit Band Center Age from Heisinger et al., 2000

S1 963-986 nm 3.43- 2.90 Ga

S2 962-991 nm 3.43 -2.90 Ga

S3 951-991 nm 3.49-2.84 Ga

S4 979-986 nm 3.43 -2.90 Ga

S5 964 -988 nm 3.76-3.71 Ga

S6 959-979 nm 3.49-2.84 Ga

S7 931-996 nm 3.76-3.71 Ga

S8 964-991 nm 3.49-2.84 Ga

S9 964-976 nm 3.44 Ga

S10 952-982 nm 2.84 Ga

S11 956-971 nm 3.55-3.43 Ga

S12 961-984 nm 2.44 Ga

S13 916-977 nm 3.76-3.71 Ga

Fig. 5. Band I center map of the 13 spectral units in the Mare Serenitatis. Absolute model ages have been taken from Hiesinger et al. (2000, 2003), and 2010.

144 P. Kaur et al. / Icarus 222 (2013) 137–148

Band I and Band II centers, obtained from the reflectance spec-tra of the fresh craters distributed across Mare Serenitatis, are plot-ted in a Band I center versus Band II center scatter plot of pureortho-and clino-pyroxenes given by Adams (1974) and modifiedby Cloutis and Gaffey (1991a) (Fig. 4). Band I and Band II centersof synthetic pyroxenes as obtained from Klima et al. (2007, 2010)(Source: RELAB) are also plotted in the same Band I versus BandII scatter plot as shown in Fig. 4 for comparison purpose. The com-positions of the synthetic pyroxenes from Klima et al. (2007, 2010)have been considered as a reference to have a qualitative ideaabout the compositional variability of pyroxenes in the basalts ofMare Serenitatis. The pyroxene chemistry of the study area thusappears to range from �Wo3En39Fs59 to Wo23En6Fs70 when com-pared with the synthetic pyroxene data (Klima et al., 2007, 2010)having similar band center range (Fig. 4). The band center valuesof the spectra from Mare Serenitatis typically range from �0.95to 0.99 lm for Band I and �2.06–2.23 lm for Band II absorptionfeatures respectively. Fig. 5 shows the band center map generated

for the study area to depict the variations in the band center valuesacross the spectral units. Band I center values of eastern Mare Ser-enitatis vary from 952 to 984 nm, whereas, in the western and cen-tral part of Mare Serenitatis, the Band I center range from 951 to991 nm (Fig. 5). Unit S4 is characterized by a narrow and restrictedBand I center range between 979 and 986 nm (Fig. 5), whereas unitS7 shows widest range of variation in terms of 1-lm absorptionband center ranging from low- to high-Ca pyroxene domain(931–996 nm) (Fig. 5).

Fig. 6 shows plot of band I center versus BAR value indicatingthat the data from the study area mostly plots vertically offset tothe BA and OC regions of Gaffey et al. (2002). The observed verticaloffset in Fig. 6 could be attributed to the higher Ca content. How-ever, the horizontal spread could be due to variety of factors suchas grain size, temperature, and mineralogical composition (Duffardet al., 2005). Most of the data points cluster around the BA regionand very few points fall within the BA, i.e., pyroxene dominated re-gion. Few of the spectral data points that lie vertically above the OC

0.90

1.00

1.10

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Ban

d I C

ente

r (um

)

Band Area Ratio

Mare Serenitatis

BA

OL

OC

Fig. 6. Band I center versus Band Area Ratio (BAR) plot, modified by Gaffey et al.(1993). Data from Mare Serenitatis plot vertically offset to the pyroxene dominatedbasaltic range (BA region).

P. Kaur et al. / Icarus 222 (2013) 137–148 145

region probably represent a clinopyroxene–olivine mixture, therespective positions of eight such data points are marked as dottedcircles in the IBD mosaic (Fig. 2) and are found to be associatedwith very bright fresh craters. The normal and continuum-re-moved reflectance spectra of these probable clinopyroxene–olivinemixtures are shown in Fig. 7a and b respectively. These bright cra-ters are mostly concentrated in the central region of Mare Sereni-tatis and are also characterized by lower BAR values (�0.93–1.43).It is evident from Fig. 7b that the probable clinopyroxene–olivinemixed spectra show relatively strong 1-lm absorption band ascompared to the 2-lm feature and are also characterized by thepresence of a weak to moderate 1.2-lm absorption feature.

Pyroxene chemistry, as obtained from the analysis of reflec-tance spectra of fresh craters based on the method outlined by Gaf-fey et al. (2002), is plotted in a pyroxene quadrilateral as shown inFig. 8. Synthetic pyroxene data of Klima et al. (2007, 2010) are alsoplotted in the pyroxene quadrilateral for comparison. From Fig. 8, itis evident that the pyroxene composition of Mare Serenitatis rangefrom sub-calcic to calcic augite. The pyroxene composition clustersaround a mean value of �Wo28En20Fs52.

0

0

0

0

0

0

1

Ref

lect

ance

0.05

0.07

0.09

0.11

0.13

0.15

0.17

0.19

0.21

0.23

0.25

500 1000 1500 2000 2500

Ref

lect

ance

Wavelength (nm)

abcdefgh

A B

Fig. 7. (a) M3 reflectance data obtained from the bright craters marked as dotted circl

6. Discussions

In this study, we have presented the spectral diversity map ofMare Serenitatis based on the IBD mosaic generated using Chan-drayaan-1 M3 L2 data. This spectral diversity map clearly depictsthe subtle variations in mafic mineralogy associated with the dif-ferent basaltic units of the mare basin. Optical maturity and feld-spathic contamination also contribute towards the spectralvariations observed in the IBD mosaic. A total of 13 spectral unitshave been identified and mapped in Mare Serenitatis based onthe spectral variations in the IBD mosaic. The spectral units are di-vided into three groups based on their locations, namely, westernand central group consisting of units S1, S2, S3, S6 and S8; easterngroup consisting of S9, S10, S11, S12 and S13 units; southwesternand southern group consisting of units S4, S5 and S7 (Fig. 2). Thespectral behavior of the units displaying yellow to greenish yellowto yellowish green color in the IBD mosaic confirms the presence ofstrong 1- and 2-lm absorption features. The blue hue in the IBDmosaic represents either materials having high albedo and contin-uum slope (optically matured) or feldspathic material of low maficcontent.

The spectral units S2, S3 and S6 appear to be free from any feld-spathic contamination due to their remote location from the high-land and also because of the absence of any prominent large craterin the vicinity (Fig. 2). The blue color of the craters in S4, S5 and S7is indicative of excavation of the feldspathic highland material ofvery low mafic content from underneath hinting towards probablya very thin mare crust adjacent to the mare-highland boundary(Fig. 2). The presence of bright blue linear array of rays around Bes-sel crater and several other craters of unit S8 could possibly be dueto the lateral mixing from a feldspathic ejecta originating outsideof Serenitatis and hence, contaminating the original lithology(e.g., Campbell et al., 1992; Bell and Hawke, 1995). Units S9 andS10 appear to be highly contaminated which is apparent from theirextremely blue diffuse appearance in the IBD mosaic (Fig. 2). How-ever, the fresh craters sampled from these units show strongabsorption having higher albedo (brighter appearance) (Fig. 2) thanother units suggesting that the fresh craters might have excavateda buried more mafic-rich crustal layer and thoroughly mixed withthe ejecta of nearby craters that might have contaminated the ori-ginal surface lithology. However, the variations near the edges ofthe individual strips can be attributed to the errors associated withthe data calibration as already discussed in Section 5.1. Unit S7 andS13 being relatively more matured than rest of the units show

.72

.77

.82

.87

.92

.97

.02

500 1000 1500 2000 2500

Wavelength (nm)

abcdefgh

es in IBD parameter image in Fig. 2; (b) continuum-removed spectra of the same.

En

HdDi

Fs

Medium Ca Pyx_KlimaLow Ca Pyx_KlimaMare Serenitatis

Fig. 8. Pyroxene quadrilateral plot showing the pyroxene compositional range of Mare Serenitatis basalts. Synthetic pyroxene data of low- and medium-Ca pyroxenes fromKlima et al. (2010) have been plotted on the pyroxene quadrilateral for comparison purpose.

146 P. Kaur et al. / Icarus 222 (2013) 137–148

weakest absorption features. The lower albedo in the unit S12(youngest unit) could be due to the lateral and/or vertical mixingthat has affected the spectral properties due to late evolution ofthis unit.

Spectra from the fresh craters within the mare basin providemore reliable information about the composition of the emplacedunit representing the original nature of the subsurface material,which, in this case, is primarily pyroxene dominated. Spectral anal-ysis has clearly brought out the variations in terms of absorptionband strength, band center values, band areas and albedo of indi-vidual fresh craters as well as the mean of the reflectance fromthe fresh craters from each of the individual spectral units (Appen-dix A and Table 2). Band center data of Mare Serenitatis pyroxenesare plotted in a Band I versus Band II scatter plot (Fig. 4), whichclearly indicates that the basaltic lithology of Mare Serenitatis isprimarily dominated by low to intermediate end of the high-Capyroxene. The absorption band centers in the pyroxene spectrashift towards the longer wavelengths with more and more substi-tution of Mg2+ by Fe2+ and Ca2+ in the pyroxene crystal structure(Adams, 1974), which is clearly observed in the spectra collectedfrom the fresh craters across Mare Serenitatis (Fig. 4) and the samehas been observed in terms of increase in the Wo and Fs contentwhen the pyroxene chemistry is plotted in a pyroxene quadrilat-eral (Fig. 8).

Some of the spectra from the very bright fresh craters (markedin Fig. 2) distributed mostly in the central part (i.e., unit S8) of themare basin show an additional absorption feature near 1.2 lmwith variable band strength. The 1.2-lm absorption feature couldbe attributed to the presence of Fe2+ in the M1 crystallographicsites of ortho- and clinopyroxenes (Klima et al., 2008) and/or oliv-ine and/or iron-bearing crystalline plagioclase. Olivine is lessabsorbing than pyroxenes and thus likely to be masked by pyrox-ene absorptions, unless the olivine is present in relatively largequantity (Singer, 1981; Pieters et al., 1980; Mustard and Pieters,1987). The presence of olivine results in a broader band I absorp-tion feature and also it displaces the Band I center towards thelonger wavelength. As is evident from Fig. 4, the Band I center val-ues for Mare Serenitatis never crossed 1-lm. However, the sam-pled spectra display moderately broad 1-lm absorption feature(Fig. 7a and b). The possibility of 1.2-lm being due to plagioclasecan be ruled out as it is unlikely that plagioclase absorption wouldbe visible in the presence of even small amounts of mafic mineralsor dark materials (e.g., Adams and Goullaud, 1978; Crown and Piet-ers, 1987). Therefore, the lower BAR values (Fig. 6) associated withthe very bright craters (Fig. 2) from the central part of Mare Sere-nitatis could be attributed to the presence of Fe-rich high-Capyroxenes having weak to moderate 1.2-lm band strengths. How-ever, the presence of olivine cannot be completely ruled out with-out comparing the laboratory mixtures of pyroxene and olivine toshow that mixtures of pyroxene and olivine could reasonably beexpected to produce the observed spectral properties.

The pyroxene composition of the Mare Serenitatis basalts, whenplotted in pyroxene quadrilateral, is found to range from

�Wo18En32Fs50 to Wo31En14Fs55 having a mean composition of�Wo28En20Fs52 indicating a sub-calcic to calcic augite composi-tional range. Pyroxenes with compositions in the middle of thequadrilateral, as observed in Fig. 8, do not represent part of anysolid solution series and might have formed at very hightemperature (�1200 �C) as a large miscibility gap exists at lowtemperature of �800 �C all along the central part of the pyroxenequadrilateral, which diminishes with increasing temperature(Perkins, 2002).

7. Summary and conclusions

The high spectral and spatial resolution M3 data from Chan-drayaan-1 mission have been utilized to map the spectral, miner-alogical and compositional variability of the basaltic units in theMare Serenitatis. IBD mosaic of Mare Serenitatis has been gener-ated to depict the variation in the mafic mineralogy to a first-order.A total of 13 spectral units have been identified and mapped in thestudy area based on the variations in the IBD mosaic. Following anIBD-based study of Mare Serenitatis, a spectral band parameterbased detailed analysis of fresh craters and matured soils has beencarried out, whereby, spectral band parameters, namely, band cen-ter, band area, band strength and band area ratio of the spectrafrom the fresh craters across Mare Serenitatis have been computed.The Band I and Band II centers, thus obtained from the reflectancespectra of the fresh craters, are plotted in a Band I versus Band IIscatter plot of pure ortho-and clino-pyroxenes given by Adams(1974) and modified by Cloutis and Gaffey (1991a). Based on thedata spread of Band I and Band II centers of the fresh craters fromMare Serenitatis in the scatter plot, it can be concluded that thepyroxene composition in Mare Serenitatis varies from low to inter-mediate end of the high-Ca pyroxene. The variable BAR values ofthe different spectral units mapped in the study area could beattributed either to the presence of pyroxene–olivine mixtures orsolely due to the presence of pyroxenes with variable 1.2-lmabsorption band. A quantitative approach has been adopted todetermine the pyroxene chemistry of the Mare Serenitatis basaltsbased on the method outlined by Gaffey et al. (2002). Quantitativeanalysis suggests a sub-calcic to calcic augite compositional rangefor Mare Serenitatis pyroxenes. No compositional trend has beenobserved in a spatial context with time across the basin, which issuggestive of a probably stable homogeneous basaltic sourceregion.

Acknowledgments

We express our sincere thanks to Dr. Peter Isaacson and theanonymous reviewer for a thorough and critical review of the ori-ginal manuscript. Thanks are due to Dr. R.R. Navalgund, FormerDirector, Space Applications Centre (ISRO), Ahmedabad and Dr.J.S. Parihar, Deputy Director, Space Applications Centre (ISRO),Ahmadabad for their constant support and encouragement. We

P. Kaur et al. / Icarus 222 (2013) 137–148 147

are also thankful to the M3 Team for providing the Level 2 reflec-tance data.

Appendix A. Supplementary material

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.icarus.2012.10.020.

References

Adams, J.B., 1974. Visible and near-infrared diffuse reflectance spectra of pyroxenesas applied to remote sensing of solid objects in the Solar System. J. Geophys.Res. 79, 4829–4836.

Adams, J.B., 1975. Interpretation of visible and near-infrared diffuse reflectancespectra of pyroxenes and other rock-forming minerals. In: Karr, C., III (Ed.),Infrared and Raman Spectroscopy of Lunar and Terrestrial Minerals. AcademicPress, New York, pp. 91–116.

Adams, J.B., Goullaud, L.H., 1978. Plagioclase feldspars: Visible and near-infrareddiffuse reflectance spectra as applied to remote sensing. Proc. Lunar Sci. Conf. 9,2901–2909.

Basu, A., 1977. Steady state, exposure age and growth of agglutinates in lunar soils.Proc. Lunar Sci. Conf. 8, 3617–3632.

Basu, A., 2005. Nanophase Fe0 in lunar soils. J. Earth Syst. Sci. 114 (3), 375–380.Bell, J.F., Hawke, B.R., 1995. Compositional variability of Serenitatis/Tranquillitatis

region of the Moon from telescopic multi-spectral imaging and spectroscopy.Icarus 118, 51–68.

Belton, J.S. et al., 1992. Lunar impact basins and crustal heterogeneity: New westernlimb and far side data from Galileo. Science 255, 570–576.

Besse, S. et al., 2011. Compositional variability of the Marius Hills volcanic complexfrom the Moon Mineralogy Mapper (M3). J. Geophys. Res. 102, 16319–16325.

Boardman, J.W. et al., 2011. Measuring moonlight: An overview of the spatialproperties, lunar coverage, selenolocation and related level 1b products of theMoon Mineralogical Mapper. J. Geophys. Res. 116, E00G14.

Burns, R.G., 1970. Mineralogical Applications of Crystal Field Theory. CambridgeUniversity Press, New York.

Burns, R.G., 1974. The polarized spectra of iron silicates: Olivine, discussion ofneglected contributions from Fe2+ ions in M(1) sites. Am. Mineral. 59, 625–629.

Burns, R.G., 1993. Mineralogical Applications of Crystal Field Theory, second ed.Cambridge University Press, Cambridge, UK, p. 551.

Bussey, D.B.J., Spudis, P., 2000. Compositional studies of the Orientale, Humorum,Nectaris, and Crisium lunar basins. J. Geophys. Res. 105, 4235–4243.

Basaltic Volcanism Study Project, 1981. Basaltic Volcanism on the TerrestrialPlanets. Pergamon Press, Inc., New York, USA, p. 1286.

Campbell, B.A., Bell, J.F., Zisk, S.H., Hawke, B.K., Horton, K.A., 1992. A high resolutionradar and CCD imaging study of crater rays in Mare Serenitatis and MareNectaris. Proc. Lunar Sci. Conf. 22, 259–274.

Clark Jr., S.P., 1957. Absorption spectra of some silicates in the visible and nearinfrared. Am. Mineral. 42, 732–742.

Clark, R.N., 1999. Spectroscopy of rocks and minerals and principles ofspectroscopy. In: Rencz, A.N. (Ed.), Manual of Remote Sensing, RemoteSensing for the Earth Sciences, vol. 3. John Wiley, New York, pp. 3–58.

Clark, R.N., Roush, T.L., 1984. Reflectance spectroscopy: Quantitative analysistechniques for remote sensing applications. J. Geophys. Res. 89, 6329–6340.

Clark, R.N., Pieters, C.M., Green, R.O., Boardman, J.W., Petro, N.E., 2011. Thermalremoval from near-infrared imaging spectroscopy data of the Moon. J. Geophys.Res. 16, E00G16.

Cloutis, E.A., 1985. Interpretive Techniques for Reflectance Spectra of Mafic Silicates.M.S. Thesis, University of Hawaii, Honolulu, Hawaii, USA.

Cloutis, E.A., Gaffey, M.J., 1991a. Pyroxene spectroscopy revisited – Spectralcompositional correlations and relationship to geothermometry. J. Geophys.Res. 96, 22809–22826.

Cloutis, E.A., Gaffey, M.J., 1991b. Spectral compositional variations in theconstituent minerals of mafic and ultra-mafic assemblages and remotesensing applications. Earth, Moon, Planets 53, 11–53.

Cloutis, E.A., Gaffey, M.J., Reed, K.L., 1986. Calibrations of phase abundance,composition, and particle size distribution for olivine–orthopyroxenemixtures from reflectance spectra. J. Geophys. Res. 91, 11641–11653.

Crown, D.A., Pieters, C.M., 1987. Spectral properties of plagioclase and pyroxenemixtures and the interpretation of lunar soil spectra. Icarus 72 (3), 492–506.

Duffard, R., Lazzaro, D., De León, J., 2005. Revisiting of spectral parameters ofsilicate-bearing meteorites. Meteorit. Planet. Sci. 40, 445–459.

Gaffey, M.J. et al., 1993. Mineralogical variations within the S-type asteroid class.Icarus 106, 573–602.

Gaffey, M.J., Cloutis, E., Kelley, M., Reed, K., 2002. Mineralogy of asteroids. In: Bottke,W.F., Cellino, A., Paolicchi, P., Binzel, R.P., Tucson (Eds.), Asteriods III. TheUniversity of Arizona Press, Tuskon, pp. 183–204.

Giguere, T.A. et al., 2003. Remote sensing studies of the Lomonosov–Fleming regionof the Moon. J. Geophys. Res. 108, E11 (5118).

Giguere, T.A. et al., 2006. Remote sensing studies of the Dionysius region of theMoon. J. Geophys. Res. 111, E06009.

Goswami, J.N., Annadurai, M., 2009. Chandrayaan-1: India’s first planetary sciencemission to the Moon. Curr. Sci. 96, 486–491.

Green, R.O. et al., 2011. The Moon Mineralogy Mapper (M3) imaging spectrometerfor lunar science: Instrumentation, calibration, and on-orbit measurementperformance. J. Geophys. Res. 116, E00G19.

Hackwill, T., 2010. Stratigraphy, evolution and volume of basalts in MareSerenitatis. Meteorit. Planet. Sci. 45, 210–219.

Hapke, B., 1975. Effects of vapor-phase deposition processes of the optical,chemical, and magnetic properties of the lunar regolith. Moon 13, 339–353.

Hapke, B., 2001. Space weathering from Mercury to the asteroid belt. J. Geophys.Res. 106, 10039–10073.

Hazen, R.M., Bell, P.M., Mao, H.K., 1978. Effects of compositional variation onabsorption spectra of lunar pyroxenes. Proc. Lunar Sci. Conf. 9, 2919–2934.

Head III, J.W., 1976. Lunar volcanism in space and time. Rev. Geophys. 14, 265–300.Head, J.W., Wilson, L., 1992. Lunar mare volcanism: Stratigraphy, eruption

conditions and the evolution of secondary crusts. Geochim. Cosmochim. Acta55, 2155–2175.

Hess, P.C., Paramentier, E.M., 1995. A model for the thermal and chemical evolutionof the moon’s interior: Implications for the onset of mare volcanism. EarthPlanet. Sci. Lett. 134, 501–504.

Hiesinger, H., Jaumann, R., Neukum, G., Head, J.W., 2000. Ages of mare basalts on thenearside. J. Geophys. Res. 105, 29239–29275.

Hiesinger, H., Head, J.W., Wolf, W., Jaumann, R., Neukum, G., 2003. Ages andstratigraphy of mare basalts in Oceanus Procellarum, Mare Nubium, MareCognitum, and Mare Insularum. J. Geophys. Res. 108, 5065.

Hiesinger, H., Head, J.W., Wolf, W., Jaumann, R., Neukum, G., 2010. Ages andstratigraphy of lunar mare basalts in Mare Frigoris and other nearside mariabased on crater size-frequency distribution measurements. J. Geophys. Res. 115,E03003.

Isaacson, P.J., Pieters, C.M., 2009. Northern Imbrium Noritic Anomaly. J. Geophys.Res. 114, E09007.

Isaacson, P.J. et al., 2011. Remote compositional analysis of lunar olivine-richlithologies with Moon Mineralogical Mapper (M3) spectra. J. Geophys. Res. 116,E00G11.

Johnson, J.R., Larson, S.M., Singer, R.B., 1991. Remote sensing of potential lunarresources: Near-side compositional properties. J. Geophys. Res. 96, 18861–18882.

King, T.V., Ridley, W.I., 1987. Relation of the spectroscopic reflectance of olivine tomineral chemistry and some remote sensing implications. J. Geophys. Res. 92,11457–11469.

Klima, R.L., Pieters, C.M., Dyar, M.D., 2007. Spectroscopy of synthetic Mg–Fepyroxenes I: Spin-allowed and spin-forbidden crystal field bands in the visibleand near-infrared. Meteorit. Planet. Sci. 42, 235–253.

Klima, R.L., Pieters, C.M., Dyar, M.D., 2008. Characterization of the 1.2-lm M1pyroxene band: Extracting cooling history from near-IR spectra of pyroxene-dominated rocks. Meteorit. Planet. Sci. 43, 1591–1604.

Klima, R.L., Dyar, M.D., Pieters, C.M., 2010. Near-infrared spectra of clinopyroxenes:Effects of calcium content and crystal structure. Meteorit. Planet. Sci. 46, 379–395.

Klima, R.L. et al., 2011. New insights into lunar petrology: Distribution andcomposition of prominent low-Ca pyroxene exposures as observed by the MoonMineralogical Mapper (M3). J. Geophys. Res. 116, E00G06.

Kodama, S., Yamaguchi, Y., 2003. Lunar mare volcanism in the eastern nearsideregion derived from Clementine UVVIS data. Meteorit. Planet. Sci. 38, 1461–1484.

Lawrence, D.J. et al., 1998. Global elemental abundance maps of the Moon: TheLunar Prospector gamma ray spectrometer. Science 281, 1484–1489.

Lawrence, D.J. et al., 2002. Iron abundances on the lunar surface as measured by theLunar Prospector Gamma-Ray and neutron spectrometers. J. Geophys. Res. E12,5130.

Lucey, P.G., Blewett, D.T., Hawke, B.R., 1998. Mapping the FeO and TiO2 content ofthe lunar surface with multispectral imagery. J. Geophys. Res. 103, 3679–3699.

Matsunaga, T. et al., 2008. Discoveries on the lithology of lunar craters central peaksby SELENE Spectral Profiler. Geophys. Res. Lett. 35, L23201.

McCord, T.B., Pieters, C.M., Feierberg, M.A., 1976. Multi-spectral mapping of thelunar surface of the lunar surface using ground-based telescopes. Icarus 29, 1–34.

McCord, T.B. et al., 1981. Moon: Near-infrared spectral reflectance: A first good look.J. Geophys. Res. 86, 10883–10892.

Morimoto et al., 1988. Nomenclature of pyroxenes. Am. Mineral., 1123–1133.Morota, T. et al., and LISM Working Group, 2008. Age determination of mare basalt

near crater Litchenberg: Preliminary results from using Selene (Kaguya) TerrainCamera Data. Lunar Planet. Sci. 39. Abstract 1514.

Mustard, J.F., Pieters, C.M., 1987. Quantitative abundance estimates frombidirectional reflectance measurements. J. Geophys. Res. 92 (B4), E617–E626.

Mustard, J.F. et al., 2011. Compositional diversity and geologic insights of theAristarchus crater from Moon Mineralogical Mapper data. J. Geophys. Res. 116,E00G12.

Noble, S.K., Pieters, C.M., Keller, L.P., 2007. An experimental approach tounderstanding the optical effects of space weathering. Icarus 192, 629–642.

Ohtake, M. et al., 2009. The global distribution of pure anorthosite on the Moon.Nature 461 (nature08317).

Papike, J.J., Hodges, F.N., Bence, A.E., 1976. Mare basalts: Crystal chemistry,mineralogy, and petrology. Rev. Geophys. Space Phys. 14, 475–540.

Perkins, D., 2002. Mineralogy, second ed. Prentice Hall, New Jersey, p. 483.

148 P. Kaur et al. / Icarus 222 (2013) 137–148

Pieters, C.M., 1977. Characterization of lunar mare basalt types-II: Spectralclassification of fresh mare craters. Proc. Lunar Sci. Conf. 8, 1037–1048.

Pieters, C.M., 1978. Mare basalt types on the front of the Moon. Proc. Lunar Sci. Conf.9, 2825–2849.

Pieters, C.M., McCord, T.B., 1976. Characterization of lunar mare basalt types: I. Aremote sensing study using reflection spectroscopy of surface soils. Proc. LunarSci. Conf. 7, 2677–2690.

Pieters, C.M., Staid, M.I., 2000. Integrated spectral analysis of Mare soils and craters:Applications to Eastern Nearside Basalts. Icarus 145, 122–139.

Pieters, C.M., Head, J.W., Adams, J.B., McCord, T.B., Zisk, S.H., Whitford-Stark, J.L.,1980. Late high-titanium basalts of the western maria: Geology of theFlamsteed region of Oceanus Procellarum. J. Geophys. Res. 85, 3913–3938.

Pieters, C.M. et al., 2000. Space weathering on airless bodies: Resolving a mysterywith lunar samples. Meteorit. Planet. Sci. 35, 1101–1107.

Pieters, C.M., Gaddis, L., Jolliff, B., Duke, M., 2001. Rock types of South Pole-Aitkenbasin and extent of basaltic volcanism. J. Geophys. Res. 106, 28001–28022.

Pieters et al., 2009. The Moon Mineralogical Mapper (M3) on Chandrayaan-1. Curr.Sci. 96, 500–505.

Ringwood, A.E., Kesson, S.E., 1976. Further limits on the bulk composition of theMoon. Lunar Planet. Sci. 7, 741–743.

Saxena, S.K., Ghose, S., 1971. Mg2+–Fe2+ order-disorder and the thermodynamics ofthe orthopyroxene crystalline solution. Am. Mineral. 56, 532–559.

Shkuratov, Y.G. et al., 2003. Composition of the lunar surface as will be seen fromSMART-1: A simulation using Clementine data. J. Geophys. Res. 108, 5020.

Singer, R.B., 1981. Near-infrared spectral reflectance of mineral mixtures:Systematic Combinations of pyroxenes, olivine, and iron oxides. J. Geophys.Res. 86 (B9), 7967–7982.

Soderblom, L.A., Arnold, J.R., Boyce, J.M., Lin, R.P., 1977. Regional variations in thelunar maria: Age, remanent magnetism, and chemistry. Proc. Lunar Sci. Conf. 8,1191–1199.

Staid, M.I., Pieters, C.M., 2001. The mineralogy of last lunar basalts: Results fromClementine. J. Geophys. Res. 106, 27887–27900.

Staid, M.I. et al., 2011. The mineralogy of last-stage lunar volcanism as observed bythe Moon Mineralogy Mapper on Chandrayaan-1. J. Geophys. Res. 106, 27877–27900.

Sunshine, J.M., Pieters, C.M., 1998. Determining the composition of olivine fromreflectance spectroscopy. J. Geophys. Res. 103, 13675–13688.

Sunshine, J.M., Hinrichs, J.L., Lucey P.G., 2000. Temperature dependence of individualabsorptions bands in olivine: Implications for inferring compositions of asteroidsurfaces from spectra. Lunar Planet. Sci. 31. Abstract 1605.

Taylor, S.A., 1989. Growth of planetary crusts. Tectonophysics 161, 147–156.Taylor, L.A., Jâkes, P., 1974. The geochemical evolution of the Moon. Proc. Lunar Sci.

Conf. 5, 1697–1722.Taylor, L.A. et al., 2001. The effects of space weathering on Apollo 17 Mare soils:

Petrographic and chemical characterization. Meteorit. Planet. Sci. 36, 285–299.

Taylor, L.A. et al., 2010. Mineralogical and chemical characterization of lunarhighland soils: Insight into the space weathering of soils on airless bodies. J.Geophys. Res. 115, E02002.

Tompkins, S., Pieters, C.M., 1999. Mineralogy of the lunar crust: Results fromClementine. Meteorit. Planet. Sci. 34, 25–41.

Wilhelms, D.E., 1987. The Geologic History of the Moon. U.S. Geol. Surv. Prof. Pap.1348, p. 302.