Near-Infrared Hyperspectral Imaging of Chang’E-5 samples in France using MicrOmega: Preliminary Results.

Introduction: China’s Chang’E-5 (CE-5) mission successfully returned ~1.73 kg of lunar samples from the northeastern region of Oceanus Procellarum in 2020 (Li et al., 2022; Zhou et al., 2022). These mare basalts (Morota et al., 2011; Qian et al., 2021; Che et al., 2021) originate from higher latitude than those explored by NASA’s Apollo and the USSR’s Luna missions, offering a unique opportunity to study previously unexamined lunar materials. As a state gift, France received 1.0 g of surface-scooped (CE5C0100) and 0.5 g of drilled material (CE5Z0800). Currently stored at the Muséum National d’Histoire Naturelle (MNHN) in Paris in a dedicated glovebox under ultra-pure nitrogen (<1 ppm O₂ and H₂O), a curation program was initiated by CNES to conduct non-invasive and non-destructive preliminary characterization of the samples before their allocation to the French scientific community.

Samples and methods: A ~90 mg powder (sub-bulk hereafter) and one millimeter-sized grain from the scooped sample were extracted into a sapphire dish within a Faculty-to-Faculty-Transfer-Container (FFTC) (Ito et al., 2020; Yada et al., 2023) inside the glovebox. Then the FFTCs were transported from MNHN to IJCLab for detailed optical imaging of the sample performed with a Keyence VHX-7000 in the MYRTHO cleanroom then transferred to the dedicated glovebox of the MicrOmega instrument installed on the PTAL setup at IAS (Bibring et al. 2017, Loizeau et al. 2021). The hyperspectral MicrOmega microscope covers the near-infrared range (0.99–3.65 µm,) with a spatial resolution of ~20 µm/pixel and a ~5 mm x 5mm field of view. Measurements were conducted in the glovebox under controlled pure-N₂ (with 150-250 ppm H₂O and 40-80 ppm O₂).

Results: Optical imaging shows that the sub-bulk sample consists of fine gray powder (a few to a few tens micron in size) with occasional bright, larger particles.  The average spectrum of the sub-bulk powder at the mm-scale exhibits a red slope typical of the lunar regolith (e.g., Pieters and Nobel 2016), starting from ~8% at 1 µm to ~18% at 2.5 µm. The spectrum also shows the olivine and pyroxene absorption feature (a right shoulder at 1 µm), and shallow absorptions around 1.3 µm, related to olivine and possibly plagioclases, and at 2 µm (pyroxene). These features are consistent with previous studies on other scooped sample from Chang’E-5 mission (e.g., Wu et al., 2024; Jiang et al., 2026). Notably, we observed a clear asymmetrical 3 µm band (centered at ~ 2.83 µm) related to H₂O with a band depth is similar to that of Chang’E-5 scooped sample measured previously under air condition (Jiang et al., 2026). At the sub-mm scale, spectra of the sub-bulk powder reveal olivine (strong 1 µm absorption), high-Ca clinopyroxene (~2.2 µm absorption), and low-Ca orthopyroxene (~1.9 µm absorption) with size varying from a few tens µm to 200-300 µm. The 3 µm absorption related to H₂O also shows some spatial variation. The large mm-sized grain reveals a complex mixture of mineralogical compositions. Detailed statistical analysis of these results will be presented at the conference.

Future plan: Ongoing work includes the analysis of the drilled sample, with similar measurements as for the scooped sample, on a fraction of the bulk powder and on mm-sized grains. We will compare the mineralogy and maturity of the samples between the two sampling sets. Additionally, we recovered small grains, with size between 50 and 300 µm, from the Teflon support during the opening of the containers. We characterized them with both the optical microscope and the FTIR I2SES facilities microscope at IAS (mid-infrared: 2.5-12.5 µm (4,000-800 cm^-1) (Duprat et al. this meeting). The larger grains will be selected for MicrOmega measurements, which will allow to link the NIR and MIR data to provide better reference information for the grain composition.

Acknowledgements:

We thank CNSA and the Chang’E-5 mission project for the gift of these lunar samples, DIM ACAV+ (Région Ile de France, C3E project), CNES (APR CE5-CURE and MicrOmega development and activities), the MARCUS project (ANR-22-EXOR-0010, PEPR Origins) for financial support. The FTIR microscope at IAS was funded by DIM-Origins (I2SES project, PI. R. Brunetto). This work used the MYRTHO clean room at IJCLab, which receives support from CNES.

References:

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