Moon feels sun’s impact

October 21, 2025

In a significant milestone for lunar science, the Indian Space Research Organisation  (ISRO)  has reported that its Chandrayaan-2 orbiter has made the first direct observation of how solar activity affects the Moon’s exosphere, the extremely thin atmosphere surrounding the lunar surface. The discovery provides new insights into lunar space weather and carries implications for future missions and human habitats on the Moon.

The observation was made using the Chandra’s Atmospheric Composition Explorer-2 (CHACE-2) instrument aboard Chandrayaan-2. On May 10, 2024, a rare solar event sent a series of Coronal Mass Ejections (CMEs) from the Sun crashing into the Moon. These eruptions caused a sharp rise in the total pressure of the dayside lunar exosphere, confirming theoretical predictions that had previously never been validated through direct measurement.

ISRO scientists noted that the number density of neutral atoms and molecules in the exosphere increased by more than tenfold during the CME event. The Moon’s exosphere, classified as a surface boundary exosphere, is particularly sensitive to solar activity because the Moon lacks a global magnetic field that could shield its surface from charged particles  and  radiation.  The CMEs amplified the release of atoms from the lunar surface, temporarily altering the composition and pressure of the surrounding exosphere.

“The Moon has a very thin atmosphere, where gas atoms and molecules rarely interact. Its exosphere is directly influenced by solar radiation, solar wind, and meteorite impacts,” ISRO explained. CMEs, which eject large amounts of solar material including helium and hydrogen ions, are especially impactful on the airless Moon. Even small variations in these factors can cause measurable changes in the exosphere.

The study, titled “Impact of a Coronal Mass Ejection on the Lunar Exosphere as Observed by CHACE-2 on the Chandrayaan-2 Orbiter,”  was  published  in Geophysical Research Letters on August 16, 2025. ISRO said that the findings not only enhance understanding of lunar space weather but also highlight the challenges for designing scientific bases on the Moon. Extreme solar events like CMEs can temporarily change atmospheric conditions, which must be considered when planning long- term human activities on the lunar surface.

This breakthrough marks a crucial step in understanding how the Moon’s environment responds to the Sun. By documenting the impact of solar coronal mass on the exosphere, Chandrayaan-2 has expanded the frontier of lunar research, providing valuable data for both scientific study and the practical planning of future lunar habitats