In a groundbreaking discovery, an instrument aboard India’s Chandrayaan-2 mission has provided the first experimental evidence confirming that solar storms, specifically Coronal Mass Ejections (CMEs), can significantly increase the density of molecules in the Moon’s exosphere — its extremely thin atmosphere. The finding, published in Geophysical Research Letters, marks a major milestone in understanding the lunar environment and its interaction with space weather.
Chandrayaan-2’s CHACE-2 Detects Lunar Exosphere Changes During Solar Storms
The discovery was made by Chandra’s Atmospheric Composition Explorer-2 (CHACE-2), one of the key payloads aboard the Chandrayaan-2 orbiter. The instrument recorded a sharp increase in the total pressure of the Moon’s sunlit exosphere during a series of powerful CMEs in May 2024, when the Sun emitted massive bursts of plasma and charged particles into space.
According to the study, authored by M.B. Dhanya of ISRO’s Vikram Sarabhai Space Centre, this increase coincided precisely with the arrival of the CME at the lunar surface. The research confirms that solar activity directly influences the composition and density of the Moon’s exosphere.
“This is the first experimental evidence for the enhancement of lunar exospheric densities during a CME,” the study states, validating a long-standing scientific prediction.
Understanding the Moon’s Fragile Exosphere
The Moon’s exosphere is not a conventional atmosphere like Earth’s. Instead, it is an extremely tenuous layer of gases and molecules that cling close to the lunar surface, created by processes such as solar radiation, solar wind bombardment, and micrometeorite impacts.
During a Coronal Mass Ejection, the Sun ejects massive clouds of charged plasma, which travel across the solar system. Unlike Earth, which has a protective magnetic field, the Moon lacks such shielding, making it highly susceptible to solar radiation. When these energetic particles collide with the lunar surface, they dislodge additional atoms and molecules, temporarily thickening the exosphere.
Key Findings and Their Implications
The CHACE-2 observations revealed that during CMEs, the exospheric pressure and density increase significantly, confirming that solar storms can dynamically alter the Moon’s near-surface environment.
Scientists believe these findings have profound implications for future lunar exploration and human settlement plans, especially as India aims to send humans to the Moon by 2040.
“Such insights are crucial for designing lunar habitats and scientific bases capable of withstanding extreme space weather conditions,” the researchers noted. “Solar events like CMEs can impact not just the lunar environment but also the safety of astronauts, surface instruments, and communication systems.”
Wider Scientific Significance
Beyond lunar science, the study offers valuable data for understanding exospheres of other celestial bodies, including Mercury, asteroids, and exoplanets. Since many such bodies also lack magnetic fields, similar processes could influence their atmospheres and surface chemistry.
By demonstrating the direct effects of solar activity on the Moon, Chandrayaan-2 has once again proven its scientific significance in advancing India’s space research capabilities. The discovery underscores the growing role of ISRO’s lunar missions in contributing to global space science and the study of space weather interactions across the solar system.
A Step Toward Safer Lunar Exploration
As India prepares for future lunar missions — including Chandrayaan-3’s extended surface studies and manned missions under the Gaganyaan and lunar base programs — these findings will play a pivotal role in ensuring astronaut safety and mission success during periods of intense solar activity.
