Raman study of shock effects in lunar anorthite from the Apollo missions

Abstract

Earth’s moon is a primary exploration target for space agencies around the world. The Moon records and preserves key information about fundamental processes that shape planetary crusts such as impact cratering. Understanding shock effects in lunar anorthite (Ca‐rich endmember of plagioclase feldspar), the principal component of anorthosite and the most common crustal mineral on the Moon, is key to the early evolution of the Moon and terrestrial planets in the solar system. However, there has not been a systematic study of shock effects in lunar anorthite using modern analytical techniques that could be used in future lunar surface exploration, such as Raman spectroscopy. This study examined 23 polished thin sections from all six Apollo missions using optical and Raman spectroscopy. We documented a variety of shock features recording low to moderate shock levels, including fractures, deformed twins, undulatory extinction, planar features, and partially isotropic plagioclase. A notable nonobservation was the absence of planar deformation features (PDFs) or completely isotropic (i.e., diaplectic glass) in this suite of samples. Raman spectroscopy results of the observed shock features show similar progressive changes in terrestrial samples: As shock level increases, band broadening, reduction of intensities, and peak loss were observed. Our Raman data are efficient in identifying shock levels and distinguishing planar features from PDFs and deformed twins, and differentiating amorphous areas from crystalline plagioclase, suggesting Raman spectroscopy as a useful tool for purposely selecting moderately to strongly shocked samples to return in future lunar missions. Our study can also help the interpretation of Raman data of impact materials from the past and future exploration missions and demonstrate the utility of Raman spectroscopy for documenting and selecting samples for future lunar missions.

Using Lunar Granulites to Constrain Re‐Equilibration Timescales of Contact Thermal Metamorphism on the Moon

“…We note that this observation may not necessarily represent the maximum shock state of the samples investigated here. Due to the heterogeneous nature of mineral shock effects on thin section scales (e.g., Pernet‐Fisher et al., 2017; Xie et al., 2021), evidence of higher pressure shock damage may be recorded in portions of the sample not included in this study.…”

Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland

“…For example, Raman spectroscopy is included as the SHERLOC instrument on the NASA Perseverance rover (Bhartia et al., 2021). Given that the surface of Mars and other airless planetary bodies have a significant cover of surface regolith generated by impact gardening (Cao et al., 2022; McKay et al., 1991; Szalay et al., 2019), developing an understanding of impact processes via Raman spectroscopy of impact sites on Earth is an important analogue for rover or lander‐based investigations carried out elsewhere in the Solar System (Wang et al., 1995; Xie et al., 2021). This is in addition to an ever‐increasing application of Raman spectroscopy for the characterization of possible biosignatures (e.g., Jorge Villar & Edwards, 2006).…”

Identification of phosphate components with different doping concentrations in various soil samples by Raman spectroscopy

“…With the deepening of lunar exploration, the identification and analysis of lunar sample composition has more important scientific research significance [1,2] . Apollo [3][4][5] , Luna [6][7][8] and Chang 'e-5 [9][10][11][12] have brought back important lunar samples from different lunar regions and carried out a series of research work. Among the main components of lunar soil, there are many kinds of phosphate minerals components, such as apatite(Ca5(PO4)3(OH, F, Cl)) and whitlockite (Ca3(PO4)2) [13][14][15][16] .…”