Lunar Geochemistry Maps

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

IIT Bombay students, working closely with experts from ISRO's U. R. Rao Satellite Center, analyzed data from the CLASS instrument on Chandrayaan-2 to obtain detailed maps of ratios of X-ray line fluxes from different elements over the surface of the Moon. The results of this work have been submitted to a reputed journal for publication. Here, we provide access to the maps, and some details about the team. 

At the bottom, we link to news coverage from various outlets.

The Technique

X-ray fluorescence (XRF) spectroscopy is a remote sensing technique utilised to study chemical composition of rocks and minerals. Solar X-rays constantly bombard the surface of the Moon and interact with the elements present, leading to characteristic fluorescence lines.

During times of heightened solar activity (like a solar flare) the intensity of these characteristic lines becomes proportionately larger and can be picked up by X-ray detectors on orbiting satellites such as the Chandrayaan-2 Large Area Soft X-ray Spectrometer. Obtaining actual chemical abundances of interest, such as percentage of silicon, calcium, magnesium etc, from these emission spectra is not a straightforward task as the observed flux depends on several factors like solar spectrum, viewing geometry, grain size, vertical layering of elements present. The multitude of uncertainties in each of these factors gets propagated to the abundances and combined with the fact that the solar spectrum (usually obtained from the XSM aboard Chandrayaan-2) can only be faithfully modelled during solar flares, creating high resolution chemical abundance maps for the whole Moon becomes a daunting task.

In our work, we circumvent the above difficulties and data gaps, by utilising ratios of integrated flux for each element's characteristic lines calculated from the CLASS's regular spatially and temporally resolved readout as a proxy for the chemical abundance. We then combine observations of the same part of the Moon from multiple orbits and create maps of ratios of line intensities of various elements which are not true chemical abundance, but as we show in our work to allow for never before achieved (with XRF) ~5 km per pixel resolution mapping and agrees with known abundance trends found independently by other methods such as UV observations and sample return missions. This is a powerful application of the Chandrayaan data and elevates prospects of XRF being used for remote sensing applications.

Researchers can download the complete data set and processing codes from zenodo. The research paper is available on arXiv.

History

This work started as a part of the Inter-IIT Tech competition held in December 2024, an annual competition amongst all IITs to come up with the best solutions to problems proposed in industry and academia. IITB's submission was chosen as the best amongst the 23 IITs that participated in this problem statement. We then worked with the URSC team and our faculty mentors to bring this project to completion for the scientific community and general public.

References

1) Details of CLASS instrument aboard Chandrayaan-2

2) 5 year review of CLASS operations

3) True elemental abundances from CLASS 

Acknowledgements

We acknowledge the use of data from the Chandrayaan-II, second lunar mission of the Indian Space Research Organisation (ISRO), archived at the Indian Space Science Data Centre (ISSDC). The data can also be accessed at the ISRO Science Data Archive.

CLASS instrument was built at UR Rao Satellite centre, Indian Space Research Organisation, Bengaluru.

The Maps

Meet the team

IIT Bombay 

URSC Team

In the news...

• IIT Bombay students chart Moon's chemistry using Chandrayaan-2 data – The Week, 23 August [ Original link | Web Archive ]

• IIT Bombay students chart Moon's chemistry using Chandrayaan-2 data – PTI, 23 August [ Original link | Web Archive ]

• IIT Bombay students chart Moon's chemistry using Chandrayaan-2 data – Economic Times, 23 August [ Original link | Web Archive ]

• IIT Bombay students decode Moon's secrets with Chandrayaan-2 data – India Today, 23 August [ Original link | Web Archive ]

• IIT Bombay students chart Moon's chemistry using Chandrayaan-2 data – The Deccan Herald, 23 August [ Original link | Web Archive ]

• IIT-B students chart Moon's chemistry using Chandrayaan-2 data – Rediff, 23 August [ Original link | Web Archive ]

• IIT Bombay maps Moon’s surface chemistry using Chandrayaan-2 data in ISRO challenge – The Telegraph, 23 August [ Original link | Web Archive ]

•  IIT Bombay students chart Moon's chemistry using Chandrayaan-2 data – The Hindu Business online, 23 August [ Original link | Web Archive ]

Hindi

• आईआईटी मुंबई ने चंद्रयान-2 के आंकड़ों के जरिये चंद्रमा के रसायन विज्ञान का मानचित्रण किया – दि प्रिंट, 23 August [ Original link | Web Archive ]

• IIT: आईआईटी बॉम्बे के छात्रों ने चांद की सतह की ‘केमिस्ट्री’ का बनाया नक्शा, चंद्रयान-2 के डेटा का किया उपयोग – अमर उजाला, 23 August [ Original link | Web Archive ]

• आईआईटी मुंबई ने चंद्रयान-2 के आंकड़ों के जरिये चंद्रमा के रसायन विज्ञान का मानचित्रण किया – IBC 24 Hindi, 23 August [ Original link | Web Archive ]

Marathi

• देशभरातल्या आयआयटींनी आयोजित केलेल्या स्पर्धेत आयआयटी मुंबईच्या विद्यार्थ्यांनी पटकावलं पहिलं स्थान – All India Radio news, 23 August [ Original Link | Web Archive ]