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Impact remnants rich in carbonaceous chondrites detected on the Moon by the Chang’e-4 rover

Abstract

The Moon has experienced an intense bombardment history since its formation1. Fragments of the impactor can remain on the lunar surface2,3,4 and can provide evidence of the evolution of the impactor composition and impact population in the Earth–Moon system3,4,5. However, the retained impactor fragments previously identified in the Apollo samples have been well mixed into bulk lunar regolith due to the subsequent impact gardening, and their properties cannot be easily isolated3,6,7. Here we report observations of a two-metre-sized crater that formed less than one million years ago obtained by the Yutu-2 rover of Chang’e-4. Hyperspectral images in the visible and near-infrared range (0.45–0.945 μm) with a spatial resolution less than 1 mm per pixel highlight the presence of glassy material with high concentration (47%) of carbonaceous chondrites. We identify this material as remnants of the original impactor that was not entirely vaporized by the impact. Although carbonaceous chondrite fragments have been found in Apollo samples8,9, no carbonaceous chondrite remnant had been directly observed on the lunar surface by remote sensing exploration. We suggest that carbonaceous chondrite-like bodies may still provide one of the sources of water to the present Moon.

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Fig. 1: Images and reflectance spectra of the targeted small crater.
Fig. 2: Spectral slope analysis results.
Fig. 3: Spectral analysis results.
Fig. 4: The digital elevation model of the 2 m crater and the iSALE simulation of crater formation.

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Data availability

The original Chang’e-4 data used in this work are available at the Data Publishing and Information Service System of China’s Lunar Exploration Program (http://moon.bao.ac.cn/index_en.jsp). The corresponding data IDs are listed in Supplementary Table 9. The endmember spectra used for spectral unmixing are from the the RELAB spectral database (http://www.planetary.brown.edu/relab/) and the spectral file IDs are listed in Supplementary Table 1. Source data are provided with this paper.

Code availability

The code used in this work is available from the corresponding author upon reasonable request.

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Acknowledgements

The Chang’e-4 mission was carried out by the Chinese Lunar Exploration Program, and the data were provided by the China National Space Administration. We thank the Chang’e-4 engineering team for their tremendous efforts to make such a successful mission possible. This work was supported by the National Natural Science Foundation of China (grant numbers 11941001, 42002306 and 42072337), the Strategic Priority Research Program of Chinese Academy of Sciences (grant number XDB41000000) and the Civil Aerospace Pre-research Project (grant numbers D020201, D020203 and D020204). Y.Y. also acknowledges support from the China Postdoctoral Science Foundation (grant number 2019TQ0323) and the Pandeng Program of the National Space Science Center, Chinese Academy of Sciences. M.-H.Z. was supported by the Science and Technology Development Fund, Macau (grant numbers 0079/2018/A2 and 0020/2021/A1) and the Civil Aerospace Presearch Project (grant number D020202). B.W. was supported by a grant from the Research Grants Council of Hong Kong (RIF project number R5043-19). We acknowledge the developers of iSALE and the pySALEPlot visualization package.

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Authors and Affiliations

Authors

Contributions

Y.L. conceived the research. Y.Y., S.L. and Y.L. performed the data analysis and wrote the manuscript. M.-H.Z. conducted the impact cratering simulation with iSALE and contributed to manuscript writing. B.W. contributed to the photogrammetric processing of PCAM images to generate the DEM of the study area. J.D. and W.F. estimated the crater age on the basis of the crater degradation model. R.X., Z.H., C.W., B.X. and J.Y. contributed to the instrument design and calibration of the spectral and the imagery data. Y.Z. contributed to manuscript writing. All authors contributed to the discussion and edited the manuscript.

Corresponding author

Correspondence to Yang Liu.

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The authors declare no competing interests.

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Peer review information Nature Astronomy thanks Brett W. Denevi, Kerri Donaldson Hanna, Katherine Joy and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Geological context of the Chang’e-4 landing area.

The mosaic of images obtained by the Lunar Reconnaissance Orbiter Camera Wide Angle Camera of the Chang’e-4 landing area. The landing site is indicated by the yellow star. The data was obtained from https://quickmap.lroc.asu.edu/.

Extended Data Fig. 2 The “glassy” materials imaged by the rover’s panorama camera.

(a) Color mosaic of PCAM images of the targeted small crater observed on the 9th lunar day at site N60. The enlarged image at bottom shows the observed glassy material. (b) The PCAM image of the crater centre observed from another direction on the 8th lunar day at site N50. (c) The relative locations of the observed “glassy” material under the rover-lander coordinate system and the two PCAM observation sites of (a) and (b).

Extended Data Fig. 3 The VNIS measurement sites on Day 9 and the corresponding CMOS images.

(a) A PCAM image mosaic showing the rover tracks and the crater rim, and all the VNIS measurement sites are marked out with green dots and the corresponding site IDs are given in yellow numbers. The blue arrow indicates the north direction. (b) The 12 reflectance images at wavelength of 560 nm obtained by the CMOS imager at the sites shown on (a), all the images are stretched from 0 to 0.2. The white circles show the field of view of the SWIR detector.

Extended Data Fig. 4 A front view of the Yutu-2 Rover taken by the terrain camera on board the Chang’e-4 lander.

The panorama cameras (PCAMs) are on top of the rover mast and the hazard avoidance cameras (HAZCAMs) are installed on the front side of the rover, close to the visible and near-infrared spectrometer (VNIS). The CMOS imager has a field of view (FOV) of 8.5° and looks down to the lunar surface from a height of ~0.7 m with a nominal fixed viewing angle of 45°, hence it can image an area of ~15 cm×21 cm. The SWIR detector only has one pixel with a FOV of 3.58° and the relative position of the SWIR field within the CMOS image is shown in the right schematic diagram. The black rectangle on the right figure represents the FOV of CMOS and the red circle within represents the FOV of SWIR detector.

Extended Data Fig. 5 Comparison of the average CMOS reflectance spectra of the different ROIs.

The average CMOS reflectance spectra within the FOV of SWIR detector. (a) The image of N66 and N55 at a wavelength of 560 nm, the white circles indicate the FOV of SWIR detector. (b) The average spectra of the corresponding ROIs shown in (a). In this work we only used the CMOS data, as the spatial resolution of the SWIR data is too low to resolve those “glassy” materials and shadow regions.

Extended Data Fig. 6 The spectra of all pixels within each ROI shown in Fig. 1d.

The spectra of single pixel are shown in gray, and the average spectra of each ROI are shown in color lines with ±1σ uncertainties determined from the statistic of the data within each ROI, respectively.

Extended Data Fig. 7 Estimated spectral slopes of all the 12 CMOS measurements on Day 9.

Estimated spectral slopes of all the 12 CMOS measurements on Day 9. On sites N65 and N66, the CMOS camera captured the “glassy” materials occurred at the crater centre. Some pixels in N65 and N66 show clearly blueing spectral trend.

Extended Data Fig. 8 The CMOS images obtained on Day 10 and corresponding spectral slope maps.

(a) The CMOS images at wavelength 560 nm obtained on Day 10. N68-N78 and N79-N90 represent images of two sites taken at varied measurement angles, respectively (ref. 15). (b) Estimated spectral slopes of the CMOS images.

Extended Data Fig. 9 Reflectance spectra of endmembers used for spectral unmixing.

(a) Reflectance spectra of endmembers used for spectral unmixing obtained from the RELAB spectral database. The detailed information of these endmembers is listed in Supplementary Table 1. (b) Enlarged view of the dashed box area shown in panel (a). (c) Reflectance spectra of agglutinate and CC normalized to 1 at 0.6 μm.

Extended Data Fig. 10 The spectral fitting results.

The spectral fitting results and corresponding CMOS images. (a) Reflectance spectra of the four typical ROIs of N65, N60, N55, and N15, and the corresponding best-fit modeling results. (b) CMOS images at wavelength of 560 nm with ROIs of N60, N55, N16, and N15. All the images are stretched from 0 to 0.2. The measurement locations of N65, N60, and N55 are shown in Extended Data Fig. 3a. The ROI of N65 is the same material as that of N66 (Fig. 1d). The ROI of N60 represents the background regolith outside the crater. The ROI of N15 represents a fresh rock found on the 3rd lunar day of the mission’s operation.

Supplementary information

Supplementary Information

Supplementary Figs. 1–4 and Tables 1–6, 8 and 9.

Supplementary Table 7

Similarities between spectra of N66 and different CC samples.

Supplementary Table 10

Reflectance of endmembers.

Supplementary Table 11

Corrected reflectance of ROIs shown in Fig. 1d and Extended Data Fig. 10b.

Source data

Source Data Fig. 4

DEM image data and impact simulation data. DEM profile data.

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Yang, Y., Li, S., Zhu, MH. et al. Impact remnants rich in carbonaceous chondrites detected on the Moon by the Chang’e-4 rover. Nat Astron 6, 207–213 (2022). https://doi.org/10.1038/s41550-021-01530-w

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