Chandrayaan-2 makes surprising discovery about the Moon's ionosphere

Bengaluru: In a groundbreaking discovery, scientists from the Space Physics Laboratory at Vikram Sarabhai Space Centre (VSSC) have found surprisingly high electron densities in the moon’s atmosphere when it moves into earth’s extended magnetic field, known as the geomagnetic tail.

This discovery challenges previous assumptions about how plasma, electrically charged gas, behaves in the lunar environment and is significant for future lunar missions.

The study, based on data from India’s Chandrayaan-2 (CH-2) orbiter, suggests that the moon’s weak magnetic fields, known as crustal magnetic fields, could be playing a much bigger role in trapping plasma than previously thought. 

Scientists tracked radio signals sent from Chandrayaan-2 as they passed through the moon’s plasma layer. These signals were received at the Indian Deep Space Network (IDSN) in Bengaluru.

The density of the plasma alters the signal as it passes through it. By analyzing how these signals changed, scientists calculated that the moon’s electron density in this region is around 23,000 electrons per cubic centimeter, nearly 100 times higher than what is found on the sunlit side of the moon.

This was unexpected because, when the moon moves into earth’s geomagnetic tail, it is shielded from the solar wind. Scientists had assumed this would lead to lower plasma densities, but the new data shows the opposite.

The research suggests that the moon’s crustal magnetic fields may be trapping plasma, preventing it from escaping and creating localized high-density regions. To confirm this, scientists used a special computer model called the 3D Lunar Ionospheric Model (3D-LIM), which showed that these high plasma densities are possible only when crustal magnetic fields are present.

This discovery is crucial for upcoming crewed and robotic lunar missions. High plasma densities can affect radio communication, cause surface charging effects on spacecraft, and interact with lunar dust.