Context

Recently, the Scientists from Indian Space Research Organisation (ISRO) have mapped out the global distribution of sodium on the Moon’s surface.

About

• The research has been done using CLASS instrument carried by the second Indian Moon mission, Chandrayaan-2.
• It uses a large area soft X-ray spectrometer.
• This is the first effort to provide a global-scale measurement of sodium on the lunar surface using X-ray fluorescent

New Findings:

• The study found a thin veneer of sodium atoms that are weakly bound to the lunar surface apart from the minor quantities found in lunar rocks.
• These sodium atoms on the surface are liberated when enough energy is given to them by solar ultraviolet radiation and solar wind ions. 
• Sodium is the only element apart from potassium that can be observed through telescopes in the lunar atmosphere (its exosphere).
• This new map of sodium would enable understanding of the surface-exosphere

X-ray fluorescent spectra:

• X-ray fluorescence is commonly used to study the composition of materials in a non-destructive manner.
• When the sun gives out solar flares, a large amount of X-ray radiation falls on the moon, triggering X-ray fluorescence.
• The CLASS measures the energy of the X-ray photons coming from the moon and counts the total number.
• The energy of the photons indicates the atom (for instance, sodium atoms emit X-ray photons of 1.04 keV) and the intensity is a measure of how many atoms are present.