Lunar Exosphere | 23 Oct 2025

Source: TH 

India’s Chandrayaan-2 lunar orbiter has made a path-breaking scientific observation - for the first time ever, it has detected the effects of the Sun’s Coronal Mass Ejection (CME) on the Moon’s exosphere. The findings were obtained using CHACE-2 (Chandra’s Atmospheric Composition Explorer-2), one of the principal scientific instruments onboard the orbiter. 

• Lunar Exosphere: The Moon’s atmosphere is extremely thin and classified as an exosphere, where gas atoms and molecules rarely collide. Its surface forms the lower boundary of this exosphere. 
  • The lunar exosphere contains gases such as helium, argon, and neon, with traces from radioactive decay, solar wind, and meteoroid impacts. 
  • Due to its low density, it cannot retain heat, causing extreme temperature variations. 
  • This fragile atmosphere is produced by several processes, including: 
    • Interaction with solar radiation and solar wind (ions of hydrogen, helium, and heavier elements). 
    • Meteorite impacts that release atoms and molecules from the lunar surface. 
• Coronal Mass Injection: A Coronal Mass Ejection (CME) is a massive, violent expulsion of plasma (a superheated gas of protons and electrons) and magnetic fields from the Sun's outer atmosphere, the corona, that erupts outward into the solar system. 
  • It is one of the largest forms of solar activity and a major driver of space weather.