Instrument on Chandrayaan-2, CLASS, designed to detect signatures of elements in the Moon’s soil, detected charged particles during the mission. This happened during the orbiter’s passage through the “geotail”.

About Geotail

  • The region exists as a result of the interactions between the Sun and Earth. 
  • The geotail is a region in space that allows the best observations

Formation of the Geotail




  • 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.


Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS)

  • CLASS measures the Moon's X-ray Fluorescence (XRF) spectra to examine the presence of major elements such as Magnesium, Aluminium, Silicon, Calcium, Titanium, Iron, and Sodium. 
  • The XRF technique will detect these elements by measuring the characteristic X-rays they emit when excited by the Sun's rays.