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Chandrayaan-2 gauges sodium content on Moon’s surface

Chandrayaan-2 gauges sodium content on Moon’s surface: Relevance for UPSC Exam

General Studies III- Achievements of Indians in S&T

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Chandrayaan-2 gauges sodium content on Moon’s surface: Context

Scientists from ISRO have mapped out the global distribution of sodium on the Moon’s surface using the CLASS instrument (Chandrayaan-2 large area soft X-ray spectrometer) onboard of the Chandrayaan-2 mission.

This is the first effort to provide a global-scale measurement of sodium on the lunar surface using X-ray fluorescent spectra.


  • Chandrayaan-2 consisted of an Orbiter, Lander and Rover, all equipped with scientific instruments to study the moon.
  • The Orbiter would watch the moon from a 100-km orbit, while the Lander and Rover modules were to be separated to make a soft landing on the moon’s surface.
  • ISRO had named the Lander module as Vikram, after Vikram Sarabhai, the pioneer of India’s space programme, and the Rover module as Pragyaan, meaning wisdom.
  • The Orbiter part of the mission has been functioning normally. It is carrying eight instruments.
  • Each of these instruments has produced a handsome amount of data that sheds new light on the moon and offers insights that could be used in further exploration.

X-Ray Fluorescence

  • It 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.

Presence of Sodium on Moon: Significance

  • Sodium can be used as a tracer of the volatile history of the moon.
  • When compared to Earth, the moon is significantly depleted of volatile elements such as sodium.
  • The amount of volatiles on the moon today can be used to test formation scenarios of the Earth-Moon system.


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