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A first Raman study of Lunar samples

Raman spectra of lunar samples -- Raman spectra of minerals have narrow peaks. The main peaks of different major rock-forming minerals do not overlap each other. Thus, minerals can usually be identified by simple inspection of the peak positions in raw Raman spectra of mineral mixtures such as soils or rocks. We were readily able to identify mineral grains present in lunar highland and mare lunar soils.

Raman spectra of four samples of lunar soil "fines": 67511, an immature, plagioclase-rich highland soil from near North Ray Crater showing a  mild fluorescence across most of the spectrum; 71501, a submature mare soil  from the Taurus-Littrow Valley; 76501, a submature, mixed mare-highland soil from the base of the North Massif; and 73241, an immature highland soil from the landslide area near South Massif.  Raman spectra of lithic fragments from sample 67513 and 76503. The white lithic fragment consists essentially of plagioclase. That mineral dominates the spectrum of the companion breccia fragment which, despite its fine-grained nature, shows both plagioclase and small olivine peaks. Plagioclase and pyroxene peaks of roughly equal height are seen in mare basalt fragment 76503,7045, and fluorescence produces a rising background with increasing wavenumber, as in 67511. The upper 76503,7030 composite spectrum contains all the individual spectra obtained on that breccia fragment, including some individual spectra dominated by plagioclase clasts, and the lower spectrum is a composite of two spectra that are mainly of the glassy-microcrystalline matrix. Raman spectra of glassy materials show broad and weak spectral bands. The central frequencies of these bands are related to the degree of polymer- ization of the silicate glass structures.

Reference: Wang A., Jolliff B.L., and Haskin L.A. "Raman spectroscopy as a method for mineral identification on lunar robotic exploration missions", Journal of Geophysical Research (1995), Vol. 100, p21189-21199.

 

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