Chandrayaan-2’s CHANCE-2 Payload Detects ‘Argon-40’ In The Lunar Exosphere


On Thursday, the Indian Space Research Organisation said that CHANCE-2 payload on the recently launched Chandrayaan-2 has detected Argon-40 in the lunar exosphere. 

Chandrayaan-2 detected Ar-40 from an altitude of about 100 kilometres. 

40Ar is one of the isotopes of Argon (a noble gas) among the radiogenic gases on the lunar surface. 

In a statement made public on Wednesday evening, ISRO said “Argon, is an important constituent of the lunar exosphere. It originates from the radioactive disintegration of Potassium-40 (40K), which has a half-life of 1.2 X 109 years.”


The space agency further added that the radioactive 40K nuclide (present deep below the lunar surface) disintegrates and makes up Argon-40.  

40Ar then diffuses through seepages and faults and makes its way up to the lunar exosphere. The rate at which it escapes from the Moon is between 3% and 6% of its total production. 

Owing to its high escape rate, 40Ar is easily detectable. 

This is not the first time that the isotope has been studied. However, the detection of Argon-40 is quite significant for ISRO. 

Argon-40, a condensable gas, reacts differently at various pressures and temperatures. Chandrayaan-2 was able to detect it in the lunar exosphere by capturing the day-night variations of concentration.

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