Get the most updated and recent current affair content on

Argon-40 in Moon’s Atmosphere

  • Vaid's ICS, Lucknow
  • 11, Mar 2022
Image Not Found

Why in  News?

  • Recently, Chandrayaan-2 made the first observations of distribution of Argon-40 in the Moon’s atmosphere.

Key Findings

Lunar exospheric species: 

  • These observations provide insight on the dynamics of the lunar exospheric species, as well as on the radiogenic activities in the first few tens of metres below the lunar surface.

Number density: 

  • CHACE-2 observations reveal:
    • an increase in the number density of Ar-40 near the sunrise terminator,
    • a decrease through the dayside,
    • a secondary peak near sunset terminator and
    • a night-side minima.
  • This is the typical behaviour of a condensable gas.

Mid latitudes: 

  • For the mid latitude regions, CHACE-2 observations showed for the first time that the variation in the number density of Ar-40 with respect to solar longitudes are similar to that of low latitude regions, despite the differences in temperature and topography.

Spatial heterogeneity: 

  • It also reveals that the distribution in Ar-40 has significant spatial heterogeneity.

Argon Bulge:

  • There are localised enhancements (termed as Argon bulge) over several regions including the KREEP [potassium (K), rare-earth elements, and phosphorus (P)] and South Pole Aitken terrain.
  • The observations of Argon bulge by CHACE-2 are indicative of unknown or additional loss processes, Moonquakes or regions with lower activation energies, which call for a better understanding of the surface-exosphere interactions and source distributions of Ar-40.



  • ‘Exosphere’ is the outermost region of the upper atmosphere of a celestial body where the constituent atoms and molecules rarely collide with each other and can escape into space.

Earth’s moon: 

  • It features a surface-boundary-exosphere.
  • For Moon, different constituents in the exosphere are fed from the surface by a variety of processes, such as:
    • thermal desorption,
    • solar wind sputtering,
    • photo-stimulated desorption, and
    • micrometeorite impact vaporisation.

Exospheric atoms: 

  • The exospheric atoms may be lost to space by the thermal escape (also known as the Jean’s escape).
  • Also, the atoms get ionised by photo-ionisation and charge exchange with the solar wind ions.
  • Subsequently, they can be swept away by the convective electric field of the solar wind.
  • Some of these atoms/ions can also be deposited back on the lunar surface.
  • Thus, the lunar exosphere exists as a result of a dynamic equilibrium between several source and sink processes.


  • The Chandra’s Atmospheric Composition Explorer-2 (CHACE-2), a quadrupole mass spectrometer onboard Chandrayaan-2 mission, has made the first-of-its-kind observations of the global distribution of Argon-40 in the tenuous lunar exosphere
  • CHACE-2 was a sequel to the CHACE experiment on the Moon Impact Probe (MIP) of Chandrayaan-1 mission.
  • It draws heritage from the Mars Exospheric Neutral Composition Analyser (MENCA) experiment aboard the Indian Mars Orbiter Mission.


  • It was launched in July 2019 and was scheduled to be an effort aimed at landing a rover on the Lunar South Pole.
  • It was sent abroad by a geosynchronous launch vehicle, the GSLV-Mk 3.
  • Its lander Vikram carshed and prevented rover Pragyaan from successful travel on the surface of the moon.

Facts for Prelims :


The Reserve Bank of India launched a new Unified Payments Interface (UPI) payments solution for feature phone users dubbed ‘UPI123Pay’.


  • UPI was introduced in 2016 and has become one of the most used digital payments platforms in the country.
  • The volume of UPI transactions has already reached ?76 lakh crore in the current year, compared to ?41 lakh crore in FY21.
    • However, at present, efficient access to UPI is available largely via smartphones.

About UPI123Pay 

  • UPI (unified payments interface) ‘123PAY’ is a three-step method to initiate and execute services for users which will work on simple phones.
  • The new UPI-based service is designed to bring the digital payments platform closer to a significant number of feature phone mobile subscribers in the country, which is estimated to be more than 40 crore. 


  • It doesn’t need an internet connection for transactions. Customers have to link their bank account with feature phones to use this facility.
  • Feature phone users will now be able to undertake a host of transactions based on four technology alternatives.
  • They include calling an IVR (interactive voice response) number, app functionality in feature phones, missed call-based approach and also proximity sound-based payments.
  • It will lapse in February 2021 unless extended for a five-year period.