- India
- Oct 20
- Sreesha V.M
Chandrayaan-2 observes effects of Coronal Mass Ejection on Moon’s surface
The Chandrayaan-2 mission, launched in 2019, has made the first-ever observation of the effects of the Sun's Coronal Mass Ejection (CME) on the Moon using its onboard scientific instruments.
What is Coronal Mass Ejection?
• A Coronal Mass Ejection (CME) is an eruption of around a billion tonnes of particles that comes from the solar atmosphere — the corona — and travels through the solar system.
• CMEs are an important part of ‘space weather’. The particles spark aurorae on planets with atmospheres, and can cause malfunctions in some technology. They can also be harmful to unprotected astronauts.
• CMEs often occur along with solar flares (explosions on the Sun’s surface), but they can also occur spontaneously.
• The Sun can eject matter in any direction, so only some of the CMEs will actually encounter Earth.
• Their magnetic fields merge between the interplanetary magnetic field (IMF) and geomagnetic field lines. This direct link between even a small percentage of the geomagnetic field lines and the IMF results in large increases in the rate of energy transfer from the solar wind and the magnetosphere.
• Because of this, CMEs are among the most important drivers of geomagnetic storms and substorms. These substorms cause the beautiful northern and southern auroral light that often are seen in the night sky at high latitudes.
Impact of CME on 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 co-existence.
• 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 from the 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 CME.
• These effects are significant on the Moon, as Moon is an airless body, that too deprived of any global magnetic field, the presence of which would have shielded (even partially) the solar effects on its surface.
Observation using payload of Chandrayaan-2
• Launched on July 22, 2019, from Sriharikota using the GSLV-MkIII-M1 rocket, Chandrayaan-2 carried eight experiment payloads.
• On August 20, 2019, Chandrayaan-2 was successfully inserted into the elliptical orbit around the Moon.
• Although communication with the Vikram lander was lost during its September 7 landing attempt, the Orbiter remains fully operational and continues to function in a 100 km x 100 km orbit around the Moon.
• One of the payloads (on-board Chandrayan-2), Chandra’s Atmospheric Compositional Explorer 2 (CHACE 2) has recorded the effects of the Coronal Mass ejections from the Sun on the lunar exosphere.
• The primary objective of the CHACE-2 payload is to study the composition and distribution of the lunar neutral exosphere and its variability.
• 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.
• The rare opportunity to directly observe the effects of a CME impacting the Moon occurred on May 10, 2024, when a series of CMEs were hurled from the Sun toward the lunar surface.
• 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 sun lit lunar exosphere.
• Apart from pushing the edge of scientific understanding about the Moon and the lunar space weather, this observation also indicates the challenges of building scientific bases on the Moon.
• Lunar base architects need to account for such extreme events, which would temporarily alter the lunar environment, before the effects subside.
India’s lunar exploration missions
• Chandrayaan-1, India’s first mission to the Moon, was launched successfully on October 22, 2008 from Sriharikota to orbit the Moon. It played a crucial role in the discovery of water molecules on the Moon.
• Chandrayaan-2 mission was India’s first attempt to land on the lunar surface. It was launched on July 22, 2019. On September 7, Chandrayaan-2’s Vikram lander lost its contact with ISRO as it was only 2.1 km away from its designated landing spot on the Moon’s South Pole region. The lander Vikram made a hard landing on the lunar surface.
• Chandrayaan-3 was a follow-on mission to Chandrayaan-2 to demonstrate end-to-end capability in safe landing and roving on the lunar surface.
• The Moon’s South Pole region was chosen for the exploration because the lunar South Pole remains much larger than that at the North Pole.
• Indian Space Research Organisation (ISRO) successfully launched Chandrayaan-3 on July 14.
• Post its launch, Chandrayaan-3 entered into lunar orbit on August 5.
• ISRO scripted history on August 23, 2023 as Chandrayaan-3’s Lander Module touched down on the lunar surface.
• India was the fourth country to master the technology of soft-landing on the Moon after the US, China and erstwhile Soviet Union.
(The author is a trainer for Civil Services aspirants.)