In a significant advancement for lunar science, the Indian Space Research Organisation (ISRO) revealed that its lunar orbiter, Chandrayaan-2, has made groundbreaking observations of the impact of Coronal Mass Ejections (CMEs) from the Sun on the Moon”s exosphere. This observation was achieved using the Chandra”s Atmospheric Composition Explorer-2 (CHACE-2) instrument aboard the spacecraft.
On May 10, 2024, a rare solar event involving multiple CMEs struck the Moon, resulting in a notable increase in the total pressure of the sunlit lunar exosphere, which is the extremely thin atmosphere surrounding the Moon. According to ISRO, the density of neutral atoms and molecules in the exosphere surged by more than an order of magnitude, supporting theoretical predictions that had not been confirmed through direct observation until now.
The Moon”s exosphere is categorized as a surface boundary exosphere and is particularly sensitive to solar activity due to the lack of a global magnetic field. The CME event facilitated the release of atoms from the lunar surface, causing temporary changes in the Moon”s atmospheric conditions. ISRO indicated that these findings not only enhance the understanding of lunar space weather but also bear significance for future lunar missions and the design of habitats for human use on the Moon.
The research, 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 explained that the Moon”s atmosphere, often referred to as an exosphere, consists of gas atoms and molecules that rarely interact with each other despite their coexistence. This exosphere is created through various processes, including the interaction of solar radiation, solar wind, and impacts from meteorites on the Moon”s surface.
In the context of CMEs, which occur when the Sun ejects substantial amounts of its material primarily composed of Helium and Hydrogen ions, the effects are pronounced on the Moon. As an airless body devoid of a global magnetic field, the Moon is particularly vulnerable to such solar phenomena. The CMEs observed on May 10 resulted in increased solar coronal mass impacting the Moon, enhancing the process of atom ejection from its surface and subsequently elevating the total pressure in the sunlit exosphere.
This observation provides vital insights into the lunar exosphere and the effects of space weather on the Moon. Furthermore, it underscores the challenges of establishing scientific bases on the Moon, as architects must consider the potential impact of extreme solar events that can temporarily alter the lunar environment before conditions stabilize. ISRO concluded that this research is pivotal in advancing our scientific understanding of lunar dynamics and space weather interactions.
