Mineralogical and chemical properties inversed from 21-lunar-day VNIS observations taken during the Chang\u2019E-4 mission

Qinghong Zeng,Anzhen Li,Yongling Mu,Peng Lu,Shengbo Chen,Rui Dai,Congyu Yang,Yuanzhi Zhang

doi:10.1038/s41598-021-93694-8

Abstract

We report on the mineralogical and chemical properties of materials investigated by the lunar rover Yutu-2, which landed on the Von Kármán crater in the pre-Nectarian South Pole–Aitken (SPA) basin. Yutu-2 carried several scientific payloads, including the Visible and Near-infrared Imaging Spectrometer (VNIS), which is used for mineral identification, offering insights into lunar evolution. We used 86 valid VNIS data for 21 lunar days, with mineral abundance obtained using the Hapke radiative transfer model and sparse unmixing algorithm and chemical compositions empirically estimated. The mineralogical properties of the materials at the Chang’E-4 (CE-4) site referred to as norite/gabbro, based on findings of mineral abundance, indicate that they may be SPA impact melt components excavated by a surrounding impact crater. We find that CE-4 materials are dominated by plagioclase and pyroxene and feature little olivine, with 50 of 86 observations showing higher LCP than HCP in pyroxene. In view of the effects of space weathering, olivine content may be underestimated, with FeO and TiO2 content estimated using the maturity-corrected method. Estimates of chemical content are 7.42–18.82 wt% FeO and 1.48–2.1 wt% TiO2, with a low-medium Mg number (Mg # ~ 55). Olivine-rich materials are not present at the CE-4 landing site, based on the low-medium Mg #. Multi-origin materials at the CE-4 landing site were analyzed with regard to concentrations of FeO and TiO2 content, supporting our conclusion that the materials at CE-4 do not have a single source but rather are likely a mixture of SPA impact melt components excavated by surrounding impact crater and volcanic product ejecta.

Highlights

Through October 25, 2020, the Yutu-2 rover of the Chang’E-4 (CE-4) mission had toured 519.29 m up to 600 days, with the Visible and Near-Infrared Image Spectrometer (VNIS) on board the rover acquiring 106 in situ reflectance measurements (Fig. 1)
Additional data from the Yutu-2 rover have not indicated the presence of expected mantle materials at the CE-4 landing site, where materials are dominated by plagioclase (Plag) and pyroxene but include little olivine (OL), for the first three lunar d ays[6]
Mineralogy properties observed by Yutu‐2 rover

Summary

Introduction

Through October 25, 2020, the Yutu-2 rover of the Chang’E-4 (CE-4) mission had toured 519.29 m up to 600 days (for 21 lunar days), with the Visible and Near-Infrared Image Spectrometer (VNIS) on board the rover acquiring 106 in situ reflectance measurements (Fig. 1). After the CE-4’s safe landing, researchers have reported initial results by interpreting the first lunar-day VNIS data showing that the materials along the rover route are dominated by olivine and low-calcium pyroxene (LCP)—suggesting that the Yutu-2 rover may have detected the moon’s mantle m aterial[3,4].

Results

Conclusion