Prelims level : Science & Technology- Space Technology Mains level : GS-III- Awareness in the Fields of space; Achievements of Indians in Science & Technology; Indigenization of Technology.
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Why in News?

  • Recently on board with Chandrayaan-2 mission, an instrument called CLASS, designed to detect signatures of elements in the Moon’s soil, had detected charged particles during the mission.This happened in September, during the orbiter’s passage through the “geotail”.


  • The geotail is a region in space that allows the best observations.
  • The region exists as a result of the interactions between the Sun and Earth.
  • The Sun emits the solar wind, which is a continuous stream of charged particles. These particles are embedded in the extended magnetic field of the Sun.
  • Since the Earth has a magnetic field, it obstructs the solar wind plasma.
  • This interaction results in the formation of a magnetic envelope around Earth.
  • On the Earth side facing the Sun, the envelope is compressed into a region that is approximately three to four times the Earth radius.
  • On the opposite side, the envelope is stretched into a long tail, which extends beyond the orbit of the Moon. It is this tail that is called the geotail.


  • CLASS stands for Chandrayaan 2 Large Area Soft X-ray Spectrometer.
  • For the CLASS instrument seeking to detect element signatures, the lunar soil can be best observed when a solar flare provides a rich source of X-rays to illuminate the surface.
  • Secondary X-ray emission resulting from this can be detected by CLASS to directly detect the presence of key elements like Na, Ca, Al, Si, Ti and Fe.
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