Key Takeaways
- Chandrayaan-2’s CHACE-2 payload made the first-ever observation of solar CME effects on the Moon
- Total pressure in the lunar exosphere increased dramatically during the May 2024 event
- Findings validate theoretical models and have implications for future lunar missions
India’s Chandrayaan-2 lunar orbiter has achieved a major scientific breakthrough by making the first-ever observation of how the Sun’s Coronal Mass Ejections (CMEs) affect the Moon. The Chandra’s Atmospheric Composition Explorer-2 (CHACE-2) instrument recorded these groundbreaking measurements.
Unprecedented Lunar Weather Observation
The Indian Space Research Organisation (ISRO) announced on October 18, 2025, that CHACE-2 detected a significant increase in the total pressure of the dayside lunar exosphere when a CME impacted the Moon. The lunar exosphere is the Moon’s extremely thin atmosphere.
ISRO stated:
“The total number density (number of neutral atoms or molecules present in an environment per unit volume) derived from these observations showed an increase by more than an order of magnitude. This increase is consistent with earlier theoretical models, which predicted such an effect, but CHACE-2 onboard Chandrayaan-2 has observed such an effect for the first time.”
Rare Solar Event Provides Opportunity
The unique observation opportunity occurred on May 10, 2024, when the Sun emitted a series of CMEs. ISRO explained:
“This increased quantity of the solar coronal mass that impacted on the moon enhanced the process of knocking off the atoms from the lunar surface, thereby liberating them to the lunar exosphere, which manifested as the enhancement of the total pressure in the sunlit lunar exosphere.”
Implications for Lunar Science and Exploration
This discovery provides crucial insights into lunar exosphere dynamics and space weather effects on the Moon. The findings also highlight challenges for future lunar missions.
ISRO noted that apart from advancing scientific understanding, these observations indicate the difficulties in building scientific bases on the Moon. Lunar base architects must account for such extreme events that temporarily alter the lunar environment.
Chandrayaan-2 Mission Context
Launched on July 22, 2019, from Sriharikota using the GSLV-MkIII-M1 rocket, Chandrayaan-2 carried eight experiment payloads. The spacecraft successfully entered lunar orbit on August 20, 2019. However, the Vikram lander lost communication during its soft landing attempt on the lunar surface.
