The Indian lunar mission, Chandrayaan-2, has achieved a significant scientific milestone by becoming the first entity in history to directly record the immediate consequences of a solar Coronal Mass Ejection (CME) striking the Moon’s exosphere. This pivotal event, which occurred on May 10, 2024, provides crucial empirical evidence regarding how celestial bodies lacking substantial atmospheric or magnetic shielding respond to powerful solar eruptions. The data sheds essential light on the immediate physical interactions between high-energy solar plasma and unprotected surfaces in the vacuum of space.
The onboard instrument of the orbital module, known as CHACE-2 (Chandra's Atmospheric Composition Explorer-2), successfully registered a dramatic shift. It recorded a sharp densification and a corresponding rise in the overall pressure of the Moon’s daytime exosphere precisely at the moment the highly energetic plasma cloud made impact. Data released by the Indian Space Research Organisation (ISRO) confirmed that the concentration of neutral atoms and molecules within this extremely tenuous outer layer surged by more than an order of magnitude compared to typical, quiescent readings. This process, known as sputtering, where the high-velocity solar plasma essentially "knocks off" atoms from the lunar surface, provides tangible proof for theoretical models that had long awaited direct observational confirmation.
The Moon’s unique geological and atmospheric profile makes it an unparalleled natural laboratory for investigating the influence of solar activity on exposed planetary surfaces. Because the Moon is entirely devoid of a global magnetic field and lacks a dense atmosphere, it offers no natural protection. This specific configuration allows high-energy particles from the solar wind and powerful Coronal Mass Ejections to interact directly and unimpeded with the lunar regolith, providing scientists with a clear view of space weathering processes in action.
The detailed findings from this observation were formally published in the prestigious journal Geophysical Research Letters on August 16, 2025. This publication is crucial as it moves the understanding of lunar space dynamics from purely theoretical modeling into the realm of confirmed empirical science. The data gathered by Chandrayaan-2 gives the scientific community a vital baseline for comparing the effects of solar events across different celestial bodies, particularly those targeted for future exploration.
This groundbreaking discovery carries direct practical implications for planning future long-duration lunar missions, particularly those involving permanent habitats or sustained human presence. Engineers and architects designing lunar bases must now more accurately factor in the risks associated with these temporary yet significant environmental shifts triggered by CMEs. On Earth, the planet's powerful magnetosphere shields us, meaning solar events primarily manifest as disruptions to power grids and satellite communications. However, on the Moon, the direct, unmitigated impact on the surface and its ultra-thin "atmosphere" transforms into a quantifiable and critical risk factor that must be mitigated for astronaut safety, equipment longevity, and the stability of sensitive electronics.
The technical triumph of the Chandrayaan-2 orbiter, which was launched back in 2019, underscores the precision of the scientific calculations that guided the mission design. Despite the unfortunate loss of the lander module Vikram in September 2019, the orbital component continues to operate flawlessly and routinely delivers vital, high-quality data from its vantage point. The information gathered regarding the CME interaction serves as a robust foundation for assessing long-term radiation hazards and understanding how high-energy particles interact with critical lunar infrastructure, paving the way toward establishing a safe and sustainable human presence on the Moon in the coming decades.