The Solar Wind and Particle Radiation Environment on the Surface of the Moon—New Observations from Chang’E-4

The solar wind, solar energetic particles and the galactic cosmic rays can reach the Moon almost unhindered, and interact with the lunar surface. The solar wind is partly scattered by the lunar regolith as hydrogen energetic neutral atoms, and the solar wind can also sputter heavy energetic neutral atoms out of the lunar regolith as well. While the albedo radiation, resulting from impact of the solar energetic particles and the galactic cosmic rays on the lunar regolith, are mainly composed of neutrons and gamma rays, features of the lunar surface radiation environment. The first ever in situ measurements of energetic neutral atoms and particle radiation have been carried out by Chang’E-4 on the lunar farside. Results reveal that a mini-magnetosphere is formed in the vicinity of the Moon, suggesting ENA is a new perspective to study the solar wind - Moon interaction. While the radiation measurements provide valuable information to guarantee the health of future robotic or manned missions to the Moon.