Lunar geochemistry from X-ray line flux ratios using CLASS on Chandrayaan 2

TL;DR

This study uses five years of Chandrayaan-2 X-ray data to create high-resolution global lunar geochemical maps, revealing compositional differences and potential regions of interest for future exploration.

Contribution

Developed an independent Python-based analysis method for CLASS data and produced detailed elemental ratio maps at 5.3 km resolution.

Findings

Mg/Al map effectively differentiates lunar terranes

Strong correlation between line ratios and elemental abundances

Gaussian mixture models identify geochemically distinct lunar regions

Abstract

Global lunar chemical maps are essential for understanding the origin and evolution of the Moon, its surface characteristics, and its potential for resource extraction. Lunar elemental abundance maps have been derived using X-ray and gamma ray spectroscopy previously but are limited in coverage or have coarse spatial resolution. Here we used X-ray fluorescence line intensity of O, Mg, Al, Si, Ca and Fe derived from five years of data from the Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS) to generate global O/Si, Mg/Si, Al/Si, Mg/Al, Ca/Si and Fe/Si line intensity ratio maps at a resolution of 5.3 km/pixel. We have developed an independent data analysis methodology for CLASS, based on open source Python packages. Our analysis shows that the Mg/Al map best represents the geochemical differences between the major terranes, consistent with the findings of the Apollo 15 and 16 X-ray Fluorescence Spectrometer (XRS) maps. We have also shown a good correlation of the line intensity ratios with the abundance ratios from CLASS using published elemental abundance maps. Further, we apply Gaussian mixture models to the Mg/Si vs Al/Si density maps to map geochemically distinct regions on the Moon that could be of interest for future investigations.