TLDR: India's Chandrayaan-2 orbiter, using its CHACE-2 instrument, recorded the first direct evidence of a solar coronal mass ejection (CME) impacting the Moon’s exosphere, confirming long-standing theories about how solar activity affects the lunar environment.
What Happened
- On May 10, 2024, a coronal mass ejection (CME) from the Sun hit the Moon, causing a sharp rise in pressure and number density in the Moon’s thin atmosphere, or exosphere.
- The CHACE-2 instrument onboard India's Chandrayaan-2 orbiter recorded this event, marking the first-ever direct observation of such an effect on the Moon.
Scientific Findings
- The CME caused atoms to be knocked off the Moon’s surface into the exosphere, increasing neutral atom density by more than ten times.
- This validated theoretical models predicting that solar eruptions could alter the lunar exosphere through a process called "sputtering".
- The Moon's lack of a magnetic field or dense atmosphere makes it more vulnerable to solar events compared to Earth.
Publication and Source
- The findings were published in Geophysical Research Letters on August 16, 2025, in a study led by ISRO scientists.
- ISRO officially announced the observation between October 17-19, 2025, and it was reported widely by Indian media.
Significance and Implications
- The discovery improves understanding of the Moon’s exosphere and space weather effects.
- It offers critical data for planning future lunar missions and habitats, which must withstand similar solar events.
- This supports global efforts, including India’s upcoming Chandrayaan-4 and NASA’s Artemis program.
Context: Chandrayaan-2
- Launched on July 22, 2019, Chandrayaan-2 includes an orbiter, lander, and rover.
- Although the lander and rover failed in 2019, the orbiter remains operational, conducting key scientific observations from lunar orbit.