Chandrayaan-2 maps sodium content on Moon’s surface

October 10, 2022

For the first time, the spectrometer on Chandrayaan-2 mapped abundance of sodium on the moon.

Key facts

The x-ray spectrometer called CLASS (Chandrayaan-2 Large Area Soft X-ray Spectrometer) aboard the Chandrayaan-2 Orbiter detected a large amount of sodium on the moon for the first time.
Earlier, Chandrayaan-1 X-ray Fluorescence Spectrometer (C1XS) opened up the possibility of large amount of sodium on the Moon by detecting the element’s characteristic line in X-rays.
CLASS spectrometer, due to its improved capability and sensitivity, was able to provide clean signature of the sodium line.
The new research found that a part of the signal could be detected from a thin veneer of sodium atoms that is weakly bound to the lunar grains on the surface.
Sodium is found in the Moon’s exosphere, where atoms rarely interact. The exosphere begins at the lunar surface and spans across several thousand kilometres before merging into the interplanetary space.
If sodium atoms are part of the lunar minerals, they can easily be pushed out of the surface by the UV rays or solar winds.
The diurnal variation of the alkali element on the surface explains its continuous supply and presence in the exosphere.
Currently, sodium and potassium are the only elements that can be observed through telescopes in the lunar atmosphere (exosphere).
The new findings by the Chandrayaan-2 provides scope to study the interactions between the lunar surface and exosphere. This could help in the development of similar models for Mercury and other airless celestial bodies in the solar system.
The recent study is the first shot towards a global-scale measurement of sodium on the lunar surface using X-ray florescent spectra.

About X-ray fluorescence

X-ray florescence is commonly used to find the composition of minerals in a non-destructive manner. It is triggered when solar flares (a large amount of X-ray radiation) falls on the lunar surface. The CLASS spectrometer measures the energy of the X-ray photons emitted from the moon and counts the total number. The photon’s energy indicates the element’s atom and its intensity is used to measure of the number of atoms present.

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