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.
@article{arxiv.2508.15563,
title = {Lunar geochemistry from X-ray line flux ratios using CLASS on Chandrayaan 2},
author = {R. Kumar and Y. Rai and S. Srijan and A. Bansal and Ameya V Singh and A. Kumar and H. Mhatre and M. Goyal and S. Swain and S. Patidar and Aditya P Saikia and A. Ahmad and S. Narendranath and Netra S Pillai and R. Kashyap and V. Bhalerao},
journal= {arXiv preprint arXiv:2508.15563},
year = {2025}
}
Comments
12 pages, 9 figures. Submitted to the Planetary Science Journal