Artistic rendition of the CME hurled by the Sun towards the Moon

In a significant achievement for lunar science, the Indian Space Research Organisation (ISRO) announced that its Chandrayaan-2 Orbiter has made the world’s first recorded observation of how solar Coronal Mass Ejections (CMEs) affect the Moon.

The discovery marks a major stride in understanding how solar activity influences the Moon’s extremely tenuous atmosphere, known as the lunar exosphere, and could reshape the way scientists model space weather interactions on airless celestial bodies.

The breakthrough was made possible through the orbiter’s scientific instrument, Chandra’s Atmospheric Compositional Explorer-2 (CHACE-2). Positioned aboard the Chandrayaan-2 spacecraft since its launch on 22 July 2019 onboard the GSLV MK-III-M1 rocket from Sriharikota, CHACE-2 recorded critical data during a rare solar event that occurred on 10 May 2024. A sequence of CMEs reached the Moon at that time, causing unprecedented disturbances in the lunar exosphere.

According to the Bangalore-based space agency, the CHACE-2 payload detected a significant rise in the total surface pressure of the Moon’s dayside exosphere. The number density of neutral atoms and 
molecules increased by more than an order of magnitude during this event.

This empirical measurement validated long-standing theoretical models predicting that CMEs could substantially alter the composition and density of the lunar exosphere.

The Moon’s exosphere, a surface boundary layer consisting of sparse atoms and molecules, is extraordinarily sensitive to changes in solar activity. Without a global magnetic field to buffer it from charged particles and radiation, the Moon is directly exposed to solar winds and CME impacts.

During the May 2024 event, ISRO scientists observed that the intense solar particle stream temporarily enhanced the ejection of atoms from the lunar surface, significantly influencing atmospheric variability.

These findings have profound implications not only for lunar science but also for future exploration and habitation plans. Understanding the dynamics of the lunar exosphere under varying solar conditions is vital for designing equipment, habitats, and life-support systems capable of withstanding space weather fluctuations. It will also contribute to developing more accurate predictive models for other airless bodies across the solar system.

Although communication with the Vikram lander was lost during its descent attempt on 7 September 2019, the Chandrayaan-2 Orbiter continues to operate flawlessly in its stable 100 x 100 km lunar orbit, providing valuable data years after launch. Its extended mission life has enabled sustained observations of the lunar environment under different solar conditions, culminating in this landmark discovery.

ISRO’s study, entitled “Impact of a Coronal Mass Ejection on the Lunar Exosphere as Observed by CHACE-2 on the Chandrayaan-2 Orbiter”, was published in the journal Geophysical Research Letters on 16 August 2025. The results establish ISRO’s Chandrayaan-2 as a crucial platform for understanding the complex interactions between solar phenomena and the lunar environment, reinforcing India’s leading role in planetary and space science research.

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