Chandrayaan-2 has mapped sodium content on Moon’s surface

In news– According to ISRO, the X-ray spectrometer ‘CLASS’ on the Chandrayaan-2 Orbiter has mapped an abundance of sodium on the moon for the first time.

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Chandrayaan-2 mapped the abundance of sodium on the Moon for the very first time using CLASS (Chandrayaan-2 Large Area Soft X-ray Spectrometer).
Built at the U R Rao Satellite Centre of ISRO in Bengaluru, CLASS provides clean signatures of the sodium line thanks to its high sensitivity and performance.
Chandrayaan-1 X-ray Fluorescence Spectrometer (C1XS) detected sodium from its characteristic line in X-rays which opened up the possibility of mapping the amount of sodium on the Moon.
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.
The study found that a part of the signal could be arising from a thin veneer of sodium atoms weakly bound to the lunar grains.
These sodium atoms can be nudged out of the surface by solar wind or ultraviolet radiation more easily than if they were part of the lunar minerals.
Also shown is a diurnal variation of the surface sodium that would explain the continuous supply of atoms to the exosphere, sustaining it.
An interesting aspect that widens the interest in this alkali element is its presence in the wispy atmosphere of the moon, a region so thin that the atoms there rarely meet.
This region, termed an ‘exosphere’, begins at the surface of the moon and extends several thousand kilometres merging into the interplanetary space.
Earlier moon missions, like Apollo-11, Luna and Chang’e-5, brought back rock samples. The amount of sodium in the rocks was precisely gauged.