Chin.J.Geochem.(2012)31:128–135 DOI: 10.1007/s11631-012-0559-1

www.gyig.ac.cn www.springerlink.com

Space weathering simulation and spectrum decoding HU Sen1,2 and LIN Yangting1

1 Key Laboratory of the Earth’s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100029, China 2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China

* Corresponding author, E-mail: LinYT@mail.iggcas.ac.cn

Received September 5, 2010; accepted October 10, 2010 © Science Press and Institute of Geochemistry, CAS and Springer-Verlag Berlin Heidelberg 2012

Abstract Visible and near-infrared spectra are routinely used to achieve mineral abundances and mineral chemistry of the global surfaces of the Moon and asteroids. However, these spectra can be significantly modified by space weathering, including micrometeorite impacting, solar wind implanting and cosmic ray irradiation. In this paper we report results of laser-bombarding experiments on the Jilin ordinary chondrite, simulating micrometeorite impacting on the surface of asteroids. After laser bombardment, the spectra became significantly redder and moderately darker. With the Modified Gaussian Model (MGM) method, the absorption band positions of olivine can be decoded from the modified spectra, which are correlated with their fayalite contents. In addition, a continuum of the modified spectra can be decoded, and its slope may be used to depict the degree of space weathering. However, relative strengths of the absorption sub-bands of olivine and pyroxenes show significant variant after the bombardment, hence they cannot be used to estimate the relative abundances of high-Ca to low-Ca pyroxenes of the lunar surface and other matured surfaces of asteroids. Key words space weathering; meteorite; asteroid; spectrum; impact

1 Introduction

Space weathering is cumulative effects of various processes taking place on materials of the airless bod-ies in space environments, usually causing the visible and near-infrared spectra darker, redder and variable absorption bands (Pieters et al., 2000). Space weath-ering was originally proposed during the period of lunar explorations, and the effects on spectra were explained by the discovery of nano-phase iron (npFe0) in lunar soil (Keller and McKay, 1993). The spectra of other airless bodies, e.g. asteroid 951 Gaspra (Chap-man, 2004) and planet Mercury (Hapke, 2001), also show significant effects by space weathering, which may cause different taxonomic classifications (Hiroi, 2009).

Visible and near-infrared spectral remote sensing is one of the most indispensable techniques for deep space exploration. The spectrum characteristics, in-cluding absorption band positions, widths and areas, can be used to derive the abundances and composi-tions of major minerals from the surfaces of the airless targets, such as Moon and other asteroids (Cloutis and Gaffey, 1991; Cloutis et al., 1984, 1986, 1990a, 2006; Gaffey et al., 1993). Modified Gaussian Model

(MGM) is a method to decompose spectra into those of their constituent components. The decoded spectra of individual components can be correlated to the mineral abundances and compositions (Sunshine et al., 1990, 1999; Sunshine and Pieters, 1998). It has advantages in comparison with other empirical meth-ods based on a few parameters of the spectra that can be significantly modified by space weathering. The MGM has been successfully used to establish rela-tionships between the absorption band parameters (strength, position and width) of olivine (Nimura et al., 2006; Sunshine and Pieters, 1989, 1998) and py-roxene (Sunshine and Pieters, 1993; Sunshine et al., 1988) with the compositions and/or abundances of the minerals.

Physical processes and the mechanism of space weathering of airless bodies were not well understood, e.g. spectra of some asteroids show significant red-dening but little darkening (Moretti et al., 2007; Gaffey, 2010). Micrometeorite impact, solar wind im-plantation and galaxy cosmic ray irradiation could be the main processes of space weathering. Especially, micrometeorite impact may be the key factor to mod-ify the upper few centimeters of the lunar regolith. These micrometeorites can travel at velocities beyond

Chin.J.Geochem.(2012)31:128–135 129

100000 km/h, inducing tremendous kinetic energy to the surfaces they hit (Anand et al., 2004). The major effects of the micrometeorite impacts are to crush, pulverize, melt and evaporate rocks and minerals, and highly reduce grain size of the materials and produce various agglutinates. The npFe0 in the outermost layer of silicate minerals of the lunar soil could also induces high energy impact and continuously H+ implantation (Keller and McKay, 1993).

Hapke (1965) simulated solar wind bombard-ment, and found significant variation in the spectra. Yamada et al. (1999) used a nanosecond pulse laser to hit olivine and pyroxene, and successfully reproduced the effects of space weathering (darkening and red-dening). Similar laser bombardment experiments found npFe0 on the surface of olivine (Sasaki et al., 2001), indicating that Fe2+ can be reduced to Fe0 without H+ implantation. Ar+ irradiation to the Epinal (H5) ordinary chondrite can also make the spectra redder (Strazzulla et al., 2005). Recently, more space weathering simulation experiments by using irradia-tion of laser and other ions (Brunetto et al., 2006, 2007; Brunetto and Strazzulla, 2005) were carried out in order to clarify physical processes and mechanism of space weathering and the results were applied to explain the spectra of asteroids and Mars (Mustard and Sunshine, 1994; Sunshine et al., 1997, 1993; Sunshine and Mustard, 1994; Sunshine and Pieters, 1992).

In order to correctly decode the spectra of the Moon for the Chang’e mission, we carried out space weathering simulation by bombarding Jilin meteorite using a laser of Nd:YAG (192 nm). The visible and near-infrared spectra of the samples before and after bombardment were decoded using the modified Gaus-sian Model (MGM) method, in an attempt to achieve information of the degree of space weathering and abundances and compositions of major minerals of samples.

2 Sampling and experiment

The Jilin ordinary chondrite is a fallen meteorite, hence the samples were preserved very fresh. Jilin meteorite was the most studied ordinary chondrite by many scientists (Xie Hongsen et al., 1989; Xie Xiande and Huang Wankang, 1991; Lin Wenzhu and Gao Laizhi, 1991; Xie Xiande and Wang Daode, 1992; Wang Daode et al., 1993). It was classified as H5 type, consisting mainly of olivine (~38 vol%), pyroxene (~34 vol%), plagioclase (~10 vol%), Fe-Ni metal (~10 vol%) and sulfides (~5 vol%) with minor apatite, chromite and ilmenite (Wang Daode et al., 1993). A freshly cut thin slice of Jilin (~1 mm thick, 2.5 cm in diameter) was polished, and used in this study. The polished section was cleaned with anhydrous alcohol

in ultrasonic and then heated at 110℃ for 24 hours. Visible and infrared spectrum measurements

were carried out with UV/VIS/NIR spectrometer type Lambda 950 by Perkin Elmer Co. in the Institute of Remote Sensing Applications, Chinese Academy of Sciences. The spectrometer was equipped with a 150 mm diameter integrating sphere, a 2 mm×8 mm sized

optical beam, 5 nm spectrum resolution, and wave-length ranging from 300 to 2500 nm. Background was corrected with fluoride. Lambda 950 has different measurement models between visible and near-infra-red regions, introducing a dis-continuum around 860 nm. For this reason, this work was focused on near-infrared spectra in a range of 860–2000 nm that covering the major absorption bands of olivine, py-roxenes and plagioclase. We measured the spectra of the Jilin samples before and after laser irradiation and compared the results to find variations.

Laser irradiation was carried out in the State Key Laboratory of Lithosphere Evolution of Institute of Geology and Geophysics, Chinese Academy of Sci-ences, using the Nd-YAG solid laser with wavelength of 193 nm. The operating conditions are 160 μm in beam size, 20 Hz in frequency, 20 J/cm2 in energy density, and 100 μm/s in sample holder moving veloc-ity when ablating. Bombarded surface area is 1 cm×1.2 cm. The chamber was filled with He gas during laser bombardment.

3 Results

Fig. 1 shows the spectra of the Jilin meteorite before and after laser bombardment. They have two major absorption bands around 1 and 2 μm regions, which are attributed to the electronic transition of Fe2+ in olivine, pyroxenes and plagioclase. The laser- bombarded spectrum was shifted to lower reflectance, indicating darkening effects of the laser bombardment. Furthermore, it is noted that the degree of darkening effect is negatively correlated with the wavelength, from 3.0% at 860 nm to 0.54% at 2000 nm, and the spectrum turns reddened.

After the laser bombardment, the relative absorp-tion depth of ~1 μm band, e.g. the difference between the maximum reflectivity at ~1500 nm and the mini-mum at ~930 nm, increases from 3.0% to 4.2%. In addition, ~1 m band position slightly increases from 915 nm for the original Jilin sample to 930 nm for the laser bombarded one (Fig. 1). The relative absorption depth of ~2 μm band, e.g. the difference between the maximum of reflectivity at ~1500 nm and the mini-mum at ~1900 nm, decreases from 2.8% to 2.0%, and indicates reversal trend with those at ~1 μm band. The absorption band of ~2 μm band position significantly increases from 1900 nm for the original Jilin sample to 1950 nm for the laser bombarded one (Fig. 1).

130 Chin.J.Geochem.(2012)31:128–135

Fig. 1. Near-infrared spectra of the Jilin meteorite before (black solid

line) and after (dashed line) laser irradiation.

4 Discussion

Firstly, we briefly introduce the spectra of the major minerals in ordinary chondrites and Modified Gaussian Model (MGM).

Olivine: Olivine is a magnesium-iron silicate with the formula (Mg, Fe2+)2SiO4 with minor substitu-tion by Ca, Mn, Fe3+, and Ni, and is the major mineral of most meteorites. The divalent cations in the olivine structure occupy two different six-coordinated sites that are named as M1 and M2 (Burns, 1993). The M1 site is smaller in comparison with the M2 site and is the more distorted of the two sites (Burns, 1993). The resultant site distortion causes a split in the energies of the two eg orbitals, leading to two distinctive absorp-tions at roughly 0.9 and 1.25 μm. The M2 site is a trigonally elongated octahedron, and this distortion causes the two eg orbitals being similar in energy. Thus, although there are two possible transitions to eg orbitals as well, their energies are almost same (~1.13 and ~1.08 μm, respectively) so that only a single M2 absorption feature is usually observed at ~1.1 μm. Substitution of Fe2+ for Mg moves the positions of all three olivine sub-bands to longer wavelengths (Sun-shine and Pieters, 1998).

Pyroxene: The pyroxene-group minerals share the general formula M2M1 (Si2O6) (Deer and Zuss-man, 1997), where the M1 site is octahedral and the M2 site is a quite distorted 6- to 8- coordinated site. The M1 site is smaller, and can be occupied by Al, Mg, Fe2+, Fe3+, Cr and Ti, while the M2 site may con-tain Ca, Na, Mg, Fe2+, Mn2+, Ni and Li. Crystal field bands from nearly all pyroxene group minerals arising from Fe2+ in M1 sites are similar; they occur in pairs around 1.18 μm and 0.93–0.98 μm (Adams, 1974; Burns, 1993; Cloutis and Gaffey, 1991). The M2 site is far more distorted than M1 because the metal-to-oxygen distances around the M2 site vary considerably with composition. Because M2 site dis-tortion increases the band intensity, even when Fe2+ is concentrated in the M1 site, bands are induced by a small amount of Fe2+ in the M2 site. The absorption

bands are typically located at 0.9–1 and 1.9–2 μm (Burns, 1993). These two bands are usually thought to be the “typical” absorption features for pyroxene. The replacement of smaller Fe2+ by larger Ca2+ causes the M2 site to inflate slightly, inducing crystal field bands moving to longer wavelengths (Burns, 1993).

Fe-Ni metal: Fe-Ni metal has no absorption fea-tures in the visible and near-infrared regions, with a monotonically increasing spectrum (Cloutis et al., 2008, 1990b). In many studies of asteroid spectra, the continuum was explicitly removed and only the sili-cate fraction was considered, with the metal fraction ignored. Fe-Ni metal in iron meteorites is spectrally red and becomes redder with increasing grain size (Cloutis et al., 1990b), however, Fe-Ni metal sepa-rated from ordinary chondrites is spectrally flat (Gaffey, 1986).

Plagioclase: Plagioclase is a common mineral found in meteorites and varies considerably in abun-dance. The ideal chemical formula for plagioclase is MT4O8 (Smith and Brown, 1988). The M site is rela-tively large and usually filled with Na+, K+, and Ca2+, while the T site contains Si4+ or Al3+. The crystal structure of plagioclase allows for the incorporation of only minor amounts of Fe2+. Pure samples have a rela-tively high albedo and an absorption band due to the electronic transition of Fe2+ centered between 1.2 and 1.3 μm.

Modified Gaussian Model (MGM): The Modified Gaussian Model (MGM) is a numerical tool for mod-eling the component absorption bands in the visible and near-infrared regions. MGM, developed by Sun-shine et al. (1990), has been demonstrated to be a physically realistic model for electronic transition ab-sorption bands that are well understood with crystal field theory (Burns, 1993). Sunshine et al. (1990) found that absorption bands were best fit a modified Gaussian, g(x) = s×exp [−(xn-μn)2/2σ2], where n was found to be −1 for room temperature measurements, while g(x) is expressed in terms of its center (μ), width (σ), and strength (s). The spectra are modeled as a number of absorption sub-bands superimposed onto a linear continuum in lg reflectance and energy (Sun-shine et al., 1990). MGM has been successfully used to fit the spectral features of minerals (Sunshine et al., 1997, 2000; Sunshine and Pieters, 1993), meteorites (Sunshine et al., 1993), and asteroids (Hiroi et al., 2006; Sunshine et al., 1997).

4.1 MGM deconvolution of spectrum of the fresh Jilin meteorite

As mentioned above, Jilin meteorite is mainly comprised of olivine, pyroxene, plagioclase, Fe-Ni metal and sulfide, with minor accessory minerals. Fe-Ni metal and sulfide of ordinary chondrites show

Chin.J.Geochem.(2012)31:128–135 131

flat pattern on the spectra from visible to near-infrared regions (Gaffey, 1986). On the other side, minor min-erals are very low in abundance, so we just count the major silicate minerals as spectral constituents.

Fig. 2 is the reflectance of olivine (Ol, PO- CMP-31), low-Ca pyroxene (Opx, PE-CMP-30), high-Ca pyroxene (Cpx, PP-CMP-21) and plagioclase (Pl, SC-EAC-037) from Relab database. Olivine has only one absorption band around 1 μm. Both low-Ca and high-Ca pyroxenes have 1 and 2 μm absorption bands, but absorption band positions shift towards longer wavelengths with increasing Ca content, due to Ca2+ tends to occupy the M2 site and weaken the Fe2+ vibration energy. Plagioclase has only one absorption

band around 1.3 μm. About 1 μm absorption band of olivine is the re-

sult of the electronic transition of Fe2+ in M1 (0.9 and 1.25 μm) and M2 (1.1 μm) sites, so 1 μm absorption band of olivine consists of 3 individual absorption sub-bands (Fig. 2). Similar with olivine, pyroxene has characteristic absorption bands around 1 and 2 μm as a result of the electronic transition of Fe2+ in M2 site (Fig. 2). As about 1 and 2 μm absorption band posi-tions of pyroxene shift toward longer wavelength with increasing Ca content, we chose low-Ca and high-Ca pyroxene to fit the spectra of Jilin meteorite, and gave 4 individual absorption sub-bands. Plagioclase has one absorption sub-band between 1.2 and 1.3 μm (Fig. 2).

Fig. 2. Near-infrared reflectance of olivine (Ol, PO-CMP-31), low-calcium pyroxene (Opx, PE-CMP-30), high-calcium pyroxene

(Cpx, PP-CMP-21) and plagioclase (Pl, SC-EAC-037) (cited from Relab database). All spectrum have been decoded by MGM

method into individual sub-bands. Fit curve is the sum of all of the individual sub-bands and continuum. RMS. residual error.

Table 1 Initial input parameters of Modified Gaussian Model

Mineral Olivine Plagioclase Low-Ca pyroxene High-Ca pyroxene

No. 1 3 5 6 2 7 4 8

Position (nm) 860±100 1000±100 1200±100 1300±100 900±100 1850±200 1050±100 2200±400

Width (nm) 100±300 200±300 200±100 100±100 100±300 200±400 200±300 200±400

Strength -0.1±1 -0.1±1 -0.1±1 -0.1±1 -0.1±1 -0.1±1 -0.1±1 -0.1±1

Continuum P0=0.21±0.1, P1=0±1 (P0: intercept, P1: slope, before laser bombardment)

P0=0.1±0.5, P1=0±1 (after laser bombardment)

132 Chin.J.Geochem.(2012)31:128–135

In order to improve the calculation velocity of MGM algorithm, we chose the initial inputs parame-ters as listed in Table 1 based on the crystal field the-ory and mineral chemistry. All sub-bands are num-bered from 1 to 8 according to its positions toward longer wavelength. Nos. 1, 3, and 5 belong to olivine. Nos. 2 and 7, and 4 and 8 belong to low-Ca pyroxene and high-Ca pyroxene, respectively. No. 6 belongs to plagioclase. Each individual sub-band has three key parameters, position, width and strength. The three sub-bands of olivine locate roughly at 860, 1000, and 1200 nm, respectively all with 100 nm variation ranges. The widths of those sub-bands are 100, 200, and 200 nm, with 300, 300, and 100 nm variation ranges, respectively. The strength is negative as in the natural lg scale. All sub-bands had same strength in-puts (-0.1) and enough variation ranges (±1) to fit the spectra. Similar with olivine, we determined the initial inputs parameters of low-Ca pyroxene, high-Ca py-roxene and plagioclase. Besides, MGM method needs a continuum, which usually is a linear function of wavelength or wavenumber. So we need another 2 parameters to define the continuum. We chose 0.21 as continuum intercept (P0) and 0 as continuum slope (P1), with ±0.1 and ±1 as variation ranges, respec-tively (Table 1). The MGM inversion results are shown in figure 4 and spectral inversion results are listed in Table 2.

Fig. 3. Results of Jilin polished section spectrum after MGM rever-

sion. The residual error (RMS) was shifted 0.05 for clarity. Fit curve

is the sum of all of the individual sub-bands and continuum.

Former studies (Nimura et al., 2006; Sunshine and Pieters, 1998) indicated that the fayalite contents of olivine were correlated with the positions of the 3 sub-bands (Fig. 4). The fayalite content of Jilin mete-orite is 18.6 mol% (Wang Daode et al., 1993). From Table 2, the positions of the 3 sub-bands of olivine were located at 853.9, 995.3, 1204.2 nm, respectively. Positions of 853.9 and 1204.2 nm sub-bands have a

perfect correlation with fayalite content (Fig. 4), indi-cating sub-band reversion parameters of olivine from whole rock spectrum being correlated with its compo-sition as well. However, 995.3 nm absorption sub-band significantly shifted away with the composi-tion, probably due to the influence of other minerals (e.g. the sub-band around 1000 nm of pyroxene) when decoding individual sub-bands of olivine from the whole rock spectrum. Our results support the correla-tion of fayalite content with individual sub-band posi-tions of olivine, which may be useful for asteroid spectra analysis.

Fig. 4. Correlation between olivine sub-band positions and its com-

position. JPS. Fresh sample; JLA. after laser irradiation. Other data

are cited from Nimura et al. (2006).

Similar with olivine, Sunshine and Pieters (1993) have found the empirical relationship between relative abundance of high-Ca to low-Ca pyroxenes and their 1 μm sub-bands strength ratios. H-group ordinary chondrites usually contain ~28 vol% low-Ca pyroxene and ~6 vol% high-Ca pyroxene (Hutchison, 2004). So the abundance of high-Ca relative to low-Ca pyrox-enes is 17.6%. On the other side, the sub-band strengths of high-Ca pyroxene and low-Ca pyroxene are -0.1101 and -0.0282 (Table 2), respectively, in-ducing a strength ratio of 2.5 for fresh sample (JPS). It shows significant lower than the empirical curve (Fig. 5), indicating complex correlation between the relative abundance of high-Ca to low-Ca pyroxenes and the sub-band strength ratios.

4.2 MGM deconvolution of the laser-bombarded Jilin meteorite

When fitting the spectrum of Jilin meteorite after laser irradiation, we chose the same initial input pa-rameters for MGM except for the continuum as the significant influence of laser bombardment (Fig. 1). Laser bombardment suggests Jilin meteorite experi-ence some degree of space weathering. So the contin-uum intercept of laser bombarded sample is supposed

Chin.J.Geochem.(2012)31:128–135 133

Table 2 Inversion results of Jilin meteorite spectrum using MGM

Mineral Olivine Plagioclase Low-Ca pyroxene High-Ca pyroxene

No. 1 3 5 6 2 7 4 8

Position (nm) S 853.9 995.3 1204.2 1306.3 920.1 1804.7 1047.8 1993.7

L 852.2 995.5 1199.0 1300.0 919.7 1856.6 1050.1 2149.1

Width (nm) S 96.2 199.5 201.4 101.2 118.0 315.2 199.0 211.1

L 92.9 202.6 199.2 99.4 122.0 356.3 195.8 236.8

Strength S -0.0370 -0.0803 -0.0361 -0.0096 -0.0783 -0.0999 -0.0315 -0.1072

L -0.0567 -0.1018 -0.0449 -0.0161 -0.1101 -0.1230 -0.0282 -0.1481

Continuum S P0=0.205，P1= -1.87e-7；(RMS=1.99e-3）

L P0=0.189，P1= -2.33e-6；(RMS=1.99e-3）

Note: S. Fresh section; L. after laser bombardment; RMS. residual error.

to be lower than that of fresh samples (0.1 vs. 0.21) and providing a wider variation ranges (±0.5 vs. ±0.1). The continuum slope is same with the fresh sample, allowing thoroughly redness (±1). The MGM inver-sion results are shown in Figure 6 and sub-bands pa-rameters are listed in Table 2.

Fig. 5. 1 μm pyroxene sub-band strength ratios versus relative abun-

dance of high-Ca to low-Ca pyroxenes. There is a significant gap

between fresh (JPS) and laser ablated samples (JLA) after MGM re-

version. Other data are cited from Sunshine and Pieters (1993).

The positions and widths of the sub-bands after laser irradiation vary little compared with the fresh sample (Table 2) except high-Ca pyroxene, which shows huge offset with the fresh sample, probably due to the low signal to noise ratio around 2000 nm re-gions. In contrast, the sub-band strengths after laser bombardment are significantly higher than the fresh sample; indicating absorption strengthened by laser bombardment around 1 and 2 μm regions. On the other side, the continuum intercept after laser bom-bardment is 0.189, lower than the fresh sample (0.205), proving the darken effect of laser bombard-ment. Meanwhile, continuum slope after laser bom-bardment is -2.33e-6, ~10 times higher than those of the fresh sample (-1.87e-7), indicating the redden ef-

fect of laser bombardment (Noble et al., 2001). In Table 2, the three sub-band positions of olivine

after laser bombardment are 852.2, 995.5, and 1199.0 nm, respectively, almost identical with those of the fresh sample (Fig. 4), indicating the composition of olivine. Pyroxene shows huge variation in comparison with olivine and plagioclase, especially high-Ca py-roxene, which has 150 nm positional offset at 2 μm region, probably due to the low signal of noise ratio around 2 μm regions. The sub-band parameters (ex-cept strength) around 1 μm after laser bombardment show little variation compared with the fresh sample. At 1 μm region, the strength ratio of high-Ca to low-Ca pyroxene is 3.9, almost on the empirical curve and significant higher than those of the fresh sample’s (Fig. 5). However, the 1 μm sub-bands strength ratios of fresh to laser bombarded samples have a huge dis-crepancy, suggesting the MGM algorithm cannot re-move the strength influence of laser bombardment.

Fig. 6. Results of Jilin meteorite spectrum after laser irradiation using

MGM reversion method. The residual error (RMS) was shifted 0.05

for clarity. Fit curve is the sum of all of the individual sub-bands and

continuum.

134 Chin.J.Geochem.(2012)31:128–135

5 Conclusions

(1) Laser bombardment on Jilin meteorite indi-cates laser can simulate the micrometeorite impacts and alter the spectra, inducing darkening and redden-ing effects to the reflectance and a little strengthen of sub-bands depths.

(2) MGM algorithm can separate the continuum to remove darken and redden effects of space weath-ering, but it lacks the ability to eliminate the sub-bands depths variations. The continuum intercept and slope probably indicate darken and redden effects of space weathering.

(3) Sub-band positions of olivine decoded from whole rock spectra are correlated with its composi-tions. However, the relative abundance of high-Ca to low-Ca pyroxenes of the whole rock cannot be de-duced from its sub-band strengths ratios.

Acknowledgements The authors thank Dr. Yang Xirong for his help in the spectrum measurements and Dr. Xie Liewen for the laser bombarding experiments. This study was supported by the Knowledge Innova-tion Program of the Chinese Academy of Sciences (kzcx2-yw-110, KZCX2-YW-Q08) and the Chinese National Programs for High Technology Research and Development (2009AA122201).

References

Adams J. (1974) Visible and near-infrared diffuse reflectance spectra of

pyroxenes as applied to remote sensing of solid objects in the solar

system [J]. Journal of Geophysical Research. 79, 4829–4836.

Anand M., Taylor L.A., Nazarov M.A., Shu J., Mao H.K., and Hemley R.J.

(2004) Space Weathering on Airless Planetary Bodies: Clues from the

Lunar Mineral Hapkeite [C]. Proceedings of the National Academy of

Sciences of the United States of America. 101, 6847–6851.

Brunetto R. and Strazzulla G. (2005) Elastic collisions in ion irradiation

experiments: A mechanism for space weathering of silicates [J].

Icarus. 179, 265–273.

Brunetto R., Romano F., Blanco A., Fonti S., Martino M., Orofino V., and

Verrienti C. (2006) Space weathering of silicates simulated by nano-

second pulse UV excimer laser [J]. Icarus. 180, 546–554.

Brunetto R., Roush T.L., Marra A.C., and Orofino V. (2007) Optical charac-

terization of laser ablated silicates [J]. Icarus. 191, 381–393.

Burns R.G. (1993) Mineralogical Applications of Crystal Field Theory [M].

Cambridge University Press, New York.

Chapman C.R. (2004) Space weathering of asteroid surfaces [J]. Annual

Review of Earth and Planetary Sciences. 32, 539–567.

Cloutis E.A., Gaffey M.J., Jackowski T.L., and Reed K.L. (1984) The spec-

tral properties of olivine-pyroxene mixtures. In Lunar and Planetary

Institut Science Conference [C]. pp.174–175. Lunar and Planetary In-

sititute, Houston, Texas.

Cloutis E.A., Gaffey M.J., Jackowski T.L., and Reed K.L. (1986) Calibra-

tions of phase abundance, composition, and particle size distribution

for olivine-orthopyroxene mixtures from reflectance spectra [J]. Jour-

nal of Geophysical Research. 91, 11641–11653.

Cloutis E.A., Gaffey M.J., Smith D.G.W., and Lambert R.S.J. (1990a) Re-

flectance spectra of glass-bearing mafic silicate mixtures and spectral

deconvolution procedures [J]. Icarus. 86, 383–401.

Cloutis E.A., Gaffey M.J., Smith D.G.W., and Lambert R.S.J. (1990b) Re-

flectance spectra of 'featureless' materials and the surface mineralogies

of M- and E-class asteroids [J]. Journal of Geophysical Research. 95,

281–293.

Cloutis E.A. and Gaffey M.J. (1991) Pyroxene spectroscopy revisited:

Spectral-compositional correlations and relationship to geothermome-

try [J]. Journal of Geophysical Research. 96, 22809–22826.

Cloutis E.A., Hawthorne F.C., Mertzman S.A., Krenn K., Craig M.A., Mar-

cino D., Methot M., Strong J., Mustard J.F., Blaney D.L., Bell J.F.,

and Vilas F. (2006) Detection and discrimination of sulfate minerals

using reflectance spectroscopy [J]. Icarus. 184, 121–157.

Cloutis E.A., Bailey D.T., and Hardersen P.S. (2008) Reflectance spectra of

iron meteorite powders. In Lunar and Planetary Institute Science

Conference [C]. pp.1082. Lunar and Planetary Institute, League City,

Texas.

Deer W., Howie R., and Zussman J. (1997) Rock-forming Minerals [M].

Geological Society Pub. House, Bath, UK.

Gaffey M.J. (1986) The spectral and physical properties of metal in meteor-

ite assemblages: Implications of asteroid surface materials [J]. Icarus.

66, 468–486.

Gaffey M.J., Burbine T.H., Piatek J.L., Reed K.L., Chaky D.A., Bell J.F.,

and Brown R.H. (1993) Mineralogical variations within the S-type

asteroid class [J]. Icarus. 106, 573.

Gaffey M.J. (2010) Space weathering and the interpretation of asteroid

reflectance spectra [J]. Icarus. 209, 564−574.

Hapke B. (1965) Effects of a simulated solar wind on the photometric prop-

erties of rocks and powders [J]. New York Academy Sciences Annals.

123, 711–721.

Hapke B. (2001) Space weathering from Mercury to the asteroid belt [J].

Journal of Geophysical Research. 106, 10039–10073.

Hiroi T., Abe M., Kitazato K., Abe S., Clark B.E., Sasaki S., Ishiguro M.,

and Barnouin-Jha O.S. (2006) Developing space weathering on the

asteroid 25143 Itokawa [J]. Nature. 443, 56–58.

Hiroi T. (2009) Space weathering. In 32nd Symposium on Antarctica Meteor-

ites [C]. pp.19. National Institute of Polar Research, Tokyo.

Hutchison R. (2004) Meteorites: A Petrologic, Chemical and Isotopic Syn-

thesis [M]. Cambridge University Press, London.

Keller L.P. and McKay D.S. (1993) Discovery of vapor deposits in the lunar

regolith [J]. Science. 261, 1305–1307.

Lin Wenzhu and Gao Laizhi (1991) Spectral reflectance of recently fallen

chondrites and some igneous rocks in China [J]. Chinese Journal of

Geochemistry. 10, 383–389.

Moretti P.F., Maras A., and Folco L. (2007) Space weathering, reddening

and darkening of asteroids: A complex problem [J]. Advances in Space

Research. 40, 258–261.

Mustard J.F. and Sunshine J.M. (1994) Limits on the mafic mineralogy of

Mars through MGM analysis of ISM spectra. In Lunar and Planetary

Institute Science Conference [C]. pp.961. Lunar and Planetary Insti-

tute, Houston, Texas.

Nimura T., Hiroi T., Ohtake M., Ueda Y., Abe M., and Fujiwara A. (2006)

An attempt of restricting olivine bands in the Modified Gaussian

Model. In Lunar and Planetary Science Conference [C]. pp.1600.

Chin.J.Geochem.(2012)31:128–135 135

Noble S.K., Pieters C.M., Taylor L.A., Morris R.V., Allen C.C., McKay

D.S., and Keller L.P. (2001) The optical properties of the finest frac-

tion of lunar soil: Implications for space weathering [J]. Meteoritics

and Planetary Science. 36, 31–42.

Pieters C.M., Taylor L.A., Noble S.K., Keller L.P., Hapke B., Morris R.V.,

Allen C.C., McKay D.S., and Wentworth S. (2000) Space weathering

on asteroids: A mystery resolved with lunar samples [J]. Meteoritics

and Planetary Science. 35, 1101–1107.

Sasaki S., Nakamura K., Hamabe Y., Kurahashi E., and Hiroi T. (2001)

Production of iron nanoparticles by laser irradiation in a simulation of

lunar-like space weathering [J]. Nature. 410, 555–557.

Smith J.V. and Brown W.L. (1988) Feldspar Minerals: Volume 1, Crystal

Structures, Physical, Chemical, and Microtextural Properties [M].

Springer-Verlag, Berlin.

Strazzulla G., Dotto E., Binzel R., Brunetto R., Barucci M.A., Blanco A.,

and Orofino V. (2005) Spectral alteration of the meteorite Epinal (H5)

induced by heavy ion irradiation: a simulation of space weathering ef-

fects on near-Earth asteroids [J]. Icarus. 174, 31–35.

Sunshine J.M., Pieters C.M., and Pratt S.F. (1988) Gaussian analysis of

pyroxene reflectance spectra. In Lunar and Planetary Institute Science

Conference [C]. pp.1151. Lunar and Planetary Institute. Houston,

Texas.

Sunshine J.M. and Pieters C.M. (1989) Quantitative deconvolution of the 1

μm olivine absorption feature. In Bulletin of the American Astronomi-

cal Society [C]. pp.967. American Astronomical Society, Providence,

Rhode Island.

Sunshine J.M., Pieters C.M., and Pratt S. (1990) Deconvolution of mineral

absorption bands: An improved approach [J]. Journal of Geophysical

Research. 95, 6955–6966.

Sunshine J.M. and Pieters C.M. (1992) Extracting olivine compositions

from asteroid spectra using the Modified Gaussian Model. In Bulletin

of the American Astronomical Society [C]. pp.940. American Astro-

nomical Society, Munich, Germany.

Sunshine J.M., McFadden L.A., and Pieters C.M. (1993) MGM analyses of

EETA 79001 lithologies: Implications for remote compositional inves-

tigations. In Bulletin of the American Astronomical Society [C].

pp.1135. American Astronomical Society, Boulder, Colorado.

Sunshine J.M. and Pieters C.M. (1993) Estimating modal abundances from

the spectra of natural and laboratory pyroxene mixtures using the

modified Gaussian model [J]. Journal of Geophysical Research. 98,

9075–9087.

Sunshine J.M. and Mustard J.F. (1994) Quantification of variations in the

mafic mineralogy of Mars through MGM analysis of ISM spectra. In

Bulletin of the American Astronomical Society [C]. pp. 1113. Ameri-

can Astronomical Society, Bethesda, Maryland.

Sunshine J.M., Binzel R.P., Burbine T.H., and Bus S.J. (1997) Diversity in

the iron content of olivine rich asteroids as revealed by MGM analy-

ses of new SMASSIR spectra. In Bulletin of the American Astronomi-

cal Society [C]. pp.964. American Astronomical Society, Cambridge,

Massachusetts.

Sunshine J.M. and Pieters C.M. (1998) Determining the composition of

olivine from reflectance spectroscopy [J]. Journal of Geophysical Re-

search. 103, 13675–13688.

Sunshine J.M., Pieters C.M., Pratt S.F., and McNaron-Brown K.S. (1999)

Absorption band modeling in reflectance spectra: Availability of the

Modified Gaussian Model. In Lunar and Planetary Institute Science

Conference [C]. pp.1306. Lunar and Planetary Institute, Houston,

Texas.

Sunshine J.M., Hinrichs J.L., and Lucey P.G. (2000) Temperature depend-

ence of individual absorptions bands in olivine: Implications for infer-

ring compositions of asteroid surfaces from spectra. In Lunar and

Planetary Institute Science Conference [C]. pp.1605. Lunar and Plane-

tary Institute. Houston, Texas.

Wang Daode, Liu Jingfa, Li Zhaohui, Chen Yongheng, Yi Weixi, Lin Yang-

ting, Hu Ruiying, Huang Wankang, and Dai Chengda (1993) Intro-

duction of Chinese Meteorites [M]. Science Express, Beijing (in Chi-

nese).

Xie Hongsen, Fang Hong, and Ouyang Ziyuan (1989) On the chemical

evolution of upper mantle of the early Earth: An experimental study

on melting of the silicate phase in Jilin chondrite at high pressures [J].

Chinese Journal of Geochemistry. 8, 171–178.

Xie Xiande and Huang Wankang (1991) Thermal and collision history of

Jilin (H5) and Qingzhen (EH3) chondrites [J]. Chinese Journal of

Geochemistry. 10, 109–115.

Xie Xiande and Wang Daode (1992) The behavior of Fe-Ni metal during

thermal metamorphism of the Jilin chondrite [J]. Chinese Journal of

Geochemistry. 11, 10–28.

Yamada M., Sasaki S., Nagahara H., Fujiwara A., Hasegawa S., Yano H.,

Hiroi T., Ohashi H., and Otake H. (1999) Simulation of space weath-

ering of planet-forming materials: Nanosecond pulse laser irradiation

and proton implantation on olivine and pyroxene samples [J]. Earth

Planets and Space. 51, 1255–1265.