Bengaluru, Oct 18 (NationPress) In a remarkable scientific achievement, the Indian Space Research Organisation (ISRO) has revealed that its lunar orbiter Chandrayaan-2 has recorded the first observation of the impact of Coronal Mass Ejections (CMEs) from the Sun on the Moon’s exosphere.

This groundbreaking observation utilized the Chandra’s Atmospheric Composition Explorer-2 (CHACE-2) instrument aboard the orbiter.

During a rare solar phenomenon on May 10, 2024, a series of CMEs struck the Moon, resulting in a significant rise in the total pressure of the dayside lunar exosphere, which is an extremely thin atmosphere enveloping the Moon.

ISRO scientists noted that the number density of neutral atoms and molecules in the exosphere surged by over an order of magnitude, validating theoretical predictions that had never before been confirmed through direct observation.

The Moon’s exosphere, categorized as a surface boundary exosphere, is particularly responsive to solar activity due to the absence of a global magnetic field. The CME event facilitated the release of atoms from the lunar surface, temporarily modifying the atmospheric conditions of the Moon.

ISRO indicated that these findings not only enhance our scientific understanding of lunar space weather but also carry implications for future lunar missions and the development of human habitats on the Moon.

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.

"The Moon has a very thin atmosphere, classified as an ‘exosphere’, which indicates that gas atoms and molecules in the lunar environment seldom interact despite their coexistence. The boundary of the exosphere is the Moon's surface, categorizing it as a ‘surface boundary exosphere’," ISRO stated.

The exosphere on the Moon originates from several processes, including interactions with solar radiation, solar wind (which consists of ions of Hydrogen, Helium, and a small quantity of heavier ions emitted by the Sun), along with impacts from meteorites on the lunar surface. These processes liberate atoms and molecules from the Moon's surface, contributing to the exosphere.

"In general, the Moon's exosphere is highly sensitive to even minor variations in the factors that contribute to its formation, such as the emission of solar coronal mass, known as CME (an abbreviation for Coronal Mass Ejection). CMEs occur when the Sun expels significant amounts of its material, primarily consisting of Helium and Hydrogen ions. These effects on the Moon are substantial, as the Moon is an airless body devoid of a global magnetic field, which would have provided some degree of protection against solar impacts on its surface," ISRO explained.

ISRO emphasized that the opportunity to directly observe the effects of CME on the Moon occurred on May 10, 2024, during a series of coronal mass ejections (CMEs) thrust by the Sun. This surge in solar coronal mass striking the Moon amplified the process of releasing atoms from the lunar surface, thereby introducing them into the lunar exosphere, which was reflected as an increase in total pressure in the illuminated lunar exosphere.

"This observation will offer scientific insights into the lunar exosphere and the effects of space weather on the Moon. Beyond advancing our scientific understanding of the Moon and lunar space weather (the impact of solar emissions on the Moon), this observation also highlights the challenges of constructing scientific bases on the Moon. Those designing lunar bases must consider such extreme events, which would temporarily alter the lunar environment, prior to the dissipation of these effects," ISRO concluded.