Chang’E-4 initial spectroscopic identification of lunar far-side mantle-derived materials

Abstract

Over 60 years of spacecraft exploration has revealed that the Earth’s Moon is characterized by a lunar crust1 dominated by the mineral plagioclase, overlying a more mafic (richer in iron and magnesium) mantle of uncertain composition. Both crust and mantle formed during the earliest stages of lunar evolution when late-stage accretional energy caused a molten rock (magma) ocean, flotation of the light plagioclase, sinking of the denser iron-rich minerals, such as olivine and pyroxene, and eventually solidification2. Very large impact craters can potentially penetrate through the crust and sample the lunar mantle. The largest of these craters is the approximately 2,500-kilometre-diameter South Pole-Aitken (SPA) basin3 on the lunar far side. Evidence obtained from orbiting spacecraft shows that the floor of the SPA basin is rich in mafic minerals4, but their mantle origin is controversial and their in situ geologic settings are poorly known. China’s Chang’E-4 lunar far-side lander recently touched down in the Von Kármán crater5,6 to explore the floor of the huge SPA basin and deployed its rover, Yutu-2. Here we report on the initial spectral observations of the Visible and Near Infrared Spectrometer (VNIS)7 onboard Yutu-2, which we interpret to represent the presence of low-calcium (ortho)pyroxene and olivine, materials that may originate from the lunar mantle. Geological context6 suggests that these materials were excavated from below the SPA floor by the nearby 72-km-diameter Finsen impact crater event, and transported to the landing site. Continued exploration by Yutu-2 will target these materials on the floor of the Von Kármán crater to understand their geologic context, origin and abundance, and to assess the possibility of sample-return scenarios.

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Fig. 1: Locations of the Chang’E-4 landing site and the VNIS measurements.
Fig. 2: Chang’E-4 reflectance spectra acquired by the VNIS during the first lunar day.
Fig. 3: Absorption-band positions for CE_0015 and CE_0016.
Fig. 4: Distribution of Finsen ejecta in the Von Kármán crater.

Data availability

Reflectance data for CE4_0015 and CE4_0016 are provided in Source Data. The source data for the Chang’E-2 Digital Orthophoto Map and the Chang’E-4 Terrain Camera image (Fig. 1) are available from the Data Publishing and Information Service System of China’s Lunar Exploration Program (http://moon.bao.ac.cn). LSCC data are available from LSCC (http://www.planetary.brown.edu/relabdocs/LSCCsoil.html). Datasets generated or analysed during this study are available from the corresponding author upon reasonable request.

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Acknowledgements

This research was funded by the Chang’E-4 mission of CLEP. We thank the team members of the Ground Application and Research System (GRAS), who contributed to data receiving and preprocessing.

Reviewer information

Nature thanks Rachel Klima and Patrick Pinet for their contribution to the peer review of this work.

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Authors

Contributions

C.L., D.L., B.L., X.R. and J.L. designed the research, performed data analysis and wrote the manuscript. Z.O. contributed scientific background, geological and geophysical context, and consistency of remote-sensing observation. W.Z., X. Zeng, X.T., X. Zhang and W.C. conducted data preprocessing. H.Z., Y.S. and W.W. helped with data receiving. Z.H., R.X. and R.S. helped with instrument design and data calibration.

Corresponding authors

Correspondence to Chunlai Li or Xin Ren or Jianjun Liu.

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Extended data figures and tables

Extended Data Fig. 1 Spectral comparison between CE4_0015, CE4_0016 and LSCC samples (continuum removed).

The red and blue lines represent CE4_0015 and CE4_0016. a, Comparison of CE4_0015 and CE4_0016 with mare soil (particle size <45 μm) samples: 10084, 12001, 12030, 15041, 15071, 70181, 71501, 79221. The 1-μm and 2-μm absorption bands of CE4_0015 and the 2-μm absorption band of CE4_0016 (dashed lines) obviously shifts to shorter wavelengths and differ considerably from the spectral features of the mare samples. b, Comparison of CE4_0015 and CE4_0016 with highland samples (particle size <45 μm): 14141, 14163, 14259, 14260, 61141, 61221, 62231, 64801, 67461, 67481. The 1-μm and 2-μm absorption bands of CE4_0015 and the 2-μm absorption band (dashed lines) of CE4_0016 resemble those of the highland samples. However, the 1-μm absorption band of CE4_0016 is more similar to that of basaltic soil, which can be attributed to elevated abundance of olivine (see main text). Source data

Extended Data Fig. 2 Parabola-fitting results for CE4_0015 and CE4_0016 1-μm and 2-μm absorption-band positions.

a, Reflectance of CE4_0015; the positions of the 1-μm and 2-μm bands are 949.2 nm and 1,985.9 nm, respectively. b, Reflectance of CE4_0016; the 1-μm- and 2-μm-band positions are 995.1 nm and 1,984.9 nm, respectively. The 2-μm-band centre assignment is tentative because of its weak absorption. The red and blue lines represent the wavelength ranges used for the parabola fitting of the 1-μm- and 2-μm-band centres, respectively. Source data

Extended Data Fig. 3 MGM deconvolution results of CE4_0015 spectra using four different mineral assemblages.

a, LCP + HCP + OL. b, LCP + HCP + Plag. c, LCP + Plag. d, LCP + OL. Source data

Extended Data Fig. 4 Content ratio HCP/(HCP + LCP) for CE4_0015 and CE4_0016, calculated by MGM deconvolution.

a, 1-μm result: 19% (CE4_0015) and 16% (CE4_0016). b, 2-μm results: 20% (CE4_0015) and 18% (CE4_0016). Data are from figure 7 of ref. 30, overlain on calibration lines (solid black line). Solid black symbols represent pyroxene samples of different grain size. The calibration line is defined by the relationship between the MGM-derived band-depth ratio of LCP/HCP and the content ratio of HCP/(HCP + LCP) measured in the laboratory for all grain sizes of the pyroxene samples. The MGM-derived band-depth ratios of LCP/HCP for CE4_0015 (red triangle) and CE4_0016 (green triangle) were projected onto the calibration line to estimate their corresponding content ratio of HCP/(HCP + LCP). Source data

Extended Data Fig. 5 Molar fraction of forsterite in olivine in CE4_0015 and CE4_0016.

The results were derived from VNIS spectra, overlain on calibration lines defined by the relationship between the Fo value and the absorption-band positions of olivine of various compositions (data used to plot the calibration lines are from figure 4 of ref. 37). Source data

Extended Data Fig. 6 M3 reflectance spectrum of Chang’E-4 landing site.

a, Average M3 reflectance spectra obtained using five adjacent pixels with central pixel position (64, 4,927). b, Continuum-removed spectrum; 1-μm-band position, 930.1 nm; 2-μm-band position, 2,058.66 nm. Source data

Extended Data Table 1 Performance characteristics of Chang’E-4 VNIS
Extended Data Table 2 MGM modelling parameters and errors of CE4_0015 spectra using different mineral components
Extended Data Table 3 Significance test for MGM deconvolution of CE4_0015
Extended Data Table 4 MGM modelling parameters and errors for CE4_0016

Source data

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Li, C., Liu, D., Liu, B. et al. Chang’E-4 initial spectroscopic identification of lunar far-side mantle-derived materials. Nature 569, 378–382 (2019). https://doi.org/10.1038/s41586-019-1189-0

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