Chandrayaan-2 Observes Sun’s Coronal Mass Ejection Impact on the Moon for the First Time

India’s Chandrayaan-2 lunar orbiter has made a groundbreaking observation, recording for the first time the effects of the Sun’s Coronal Mass Ejection (CME) on the Moon.

Observation Details

• The observation was made by Chandra’s Atmospheric Composition Explorer-2 (CHACE-2), a payload aboard the Chandrayaan-2 orbiter.
• Data showed a significant increase in the total pressure of the dayside lunar exosphere (the Moon’s extremely thin atmosphere) when the CME impacted the lunar surface.
• This confirmed theoretical predictions made earlier about CME interactions with the Moon but was observed directly for the first time.

Event Timeline

• The rare observation occurred on May 10, 2024, when a series of CMEs were hurled by the Sun toward the Moon.
• The enhanced solar coronal mass knocked atoms off the lunar surface, releasing them into the exosphere, causing the observed rise in exospheric pressure on the Moon’s sunlit side.

About Chandrayaan-2

• Launch Date: July 22, 2019, from Sriharikota using the GSLV-MkIII-M1 rocket
• Orbit Insertion: August 20, 2019, into an elliptical lunar orbit
• Payloads: Eight scientific instruments, including CHACE-2
• Vikram Lander: Attempted soft landing but lost communication with ground stations

Understanding Coronal Mass Ejections (CMEs)

• Definition: CMEs are huge bubbles of coronal plasma threaded with intense magnetic fields, ejected from the Sun over several hours.
• Appearance: Often resemble twisted ropes, termed flux ropes
• Occurrence: Can happen spontaneously or alongside solar flares; frequency varies with the 11-year solar cycle
  • Solar minimum: ~1 CME per week
  • Solar maximum: 2–3 CMEs per day
• Impact on Earth: CMEs disrupt solar wind and can damage space and ground-based systems

Moon’s Exosphere

• The Earth’s Moon has a very thin atmosphere, which falls under the category of ‘exosphere’, implying that the gas atoms and molecules in the lunar environment rarely interact despite their coexistence.
• The boundary of the exosphere is the surface of the Moon and hence the Moon’s exosphere falls under the category of ‘surface boundary exosphere’.
• The exosphere on the Moon is produced by a number of processes, which involves the interaction of solar radiation,solar wind (ions of Hydrogen, Helium and a small quantity of heavier ions emanated from the Sun) and the impact of the meteorites with the surface of the Moon.
• These processes liberate atoms/molecules fromthe surface of the Moon, which become a part of the exosphere.
• In general, the exosphere of the Moon is highly sensitive to even small variations of the factors that are responsible for its creation, and such a factor is the emission of the coronal mass of the Sun, known as CME (short form of Coronal Mass Ejection).

(Sources: ISRO & NASA)