Bengaluru, Oct 19, 2025: India’s Chandrayaan-2 orbiter has made the first-ever direct observation of the effects of a Coronal Mass Ejection (CME) from the Sun on the Moon, using its Chandra’s Atmospheric Composition Explorer-2 (CHACE-2) instrument.

CHACE-2 recorded a significant increase in the total pressure of the Moon’s dayside exosphere when the CME struck, with the number density of neutral atoms and molecules rising by more than an order of magnitude. This observation confirms earlier theoretical predictions, marking the first time such an effect has been measured in situ.

The Moon’s exosphere is extremely tenuous, with atoms and molecules interacting very rarely. It is primarily generated through processes such as solar radiation, solar wind, and meteoritic impacts. The Moon lacks a global magnetic field, making its surface highly sensitive to solar events like CMEs, which eject massive amounts of Helium and Hydrogen ions into space.

The observation took place on May 10, 2024, when a series of CMEs from the Sun impacted the Moon. The enhanced solar activity increased the rate at which atoms were liberated from the lunar surface, temporarily boosting the exosphere’s total pressure.

This milestone provides critical scientific insight into lunar exosphere dynamics and space weather effects on airless bodies. The findings are also significant for future lunar exploration, as planners of lunar bases must account for temporary but extreme space weather events that can alter the Moon’s environment.

This observation further strengthens India’s position in advancing planetary science and understanding of lunar space weather.