Recently, Professor Shi Quanqi’s team from Shandong University, in collaboration with international researchers, analyzed long-term observational data from the Lunar Lander Neutron and Dosimetry (LND) instrument onboard China’s Chang’E-4 lunar lander and discovered a new spatial structure in Earth–Moon space—the “galactic cosmic ray (GCR) cavity.” This finding indicates that the influence of Earth’s magnetic field on the interplanetary environment extends beyond the magnetosphere and reaches at least lunar orbit, forming a natural “shelter” region with reduced radiation from high-energy particles. The results were published in Science Advances on March 26, 2026, titled “A galactic cosmic ray cavity in Earth–Moon space.” Dr. Shang Wensai (Shandong University), Dr. Liu Ji (University of Alberta), and Dr. Xu Zigong (California Institute of Technology) are the co-first authors, and Professor Shi Quanqi (Shandong University) and Professor Robert Wimmer-Schweingruber (Kiel University) are the corresponding authors.

GCRs are high-energy charged particles originating from deep space in the galaxy. Due to their strong penetrating and ionizing capabilities, they can damage spacecraft electronics and biological tissues and represent one of the most hazardous radiation sources in deep space, for which effective shielding strategies remain limited. Traditional observations and theoretical studies have generally assumed that GCRs are nearly isotropically distributed in interplanetary space. Because of their high energies and strong penetration ability, significant natural shielding effects have been thought to occur mainly within the magnetic fields of strongly magnetized bodies. For example, Earth’s global magnetic field forms a magnetosphere that deflects and blocks charged particles, reducing radiation levels in near-Earth space and helping maintain a habitable environment on Earth’s surface. In contrast, regions outside the magnetosphere, such as Earth–Moon spaceorinterplanetary space, have long been considered to lack substantial natural radiation shielding. Therefore, radiation protection against high-energy particles remains a critical challenge for astronaut safety and spacecraft reliability in deep-space exploration.

Chang’E-4 successfully landed on the lunar far-side on January 3, 2019, marking the beginning of a new era of lunar far-side exploration. The onboard LND instrument continuously monitored the radiation environment over more than three years, effectively sampling Earth–Moon space as the Moon orbited Earth with a period of about 28 days. The research team identified a persistent region of significantly reduced GCR flux on the day-side portion of the lunar orbit, demonstrating the existence of a low-radiation “cosmic ray cavity” in Earth–Moon space (Figure 1). Independent measurements from NASA’s Lunar Reconnaissance Orbiter further confirmed this structure, and numerical simulations revealed that it arises from the modulation of GCR trajectories by Earth’s magnetic field. Analogous to a rock in a flowing stream, Earth’s magnetic field alters the motion of charged particles propagating along large-scale interplanetary magnetic field lines, creating a downstream region of reduced particle density.

Figure 1.Illustration of the formation of the GCR cavity in the ecliptic plane.

These findings demonstrate that Earth’s magnetic field can influence the spatial distribution of high-energy particles far beyond the magnetosphere, extending to Earth–Moon space. The study further suggests that similar cosmic ray cavities may exist around other strongly magnetized planets, and may provide new scientific insight and potential strategies for radiation mitigation and trajectory optimization in future deep-space and interstellar missions.

This research was supported by the National Natural Science Foundation of China and the Shandong Provincial Natural Science Foundation, among other funding sources. The Solar Wind-Magnetosphere Interaction Groupat the Institute of Space Sciences, Shandong University, has long been engaged in studies of the space environments of the Earth, the Moon, and other planets, with a strong emphasis on international collaboration. In recent years, the team has made a series of important advances, publishing more than 100 papers in leading journals such as Nature Physics, Science Advances, Nature Communications, and Space Science Reviews, and receiving multiple prestigious academic awards both domestically and internationally. The team has established a Space Particle Radiation Detection Laboratory dedicated to acquiring in situ observational data using self-developed instruments, and to conducting original and interdisciplinary research based on these data. In addition, the team has independently designed and developed a near-Earth orbit neutron and charged particle spectrometer, which was successfully launched aboard the “Weiming-1” satellite in 2024 and the “Dier-5” space experimental platform in 2025. Further information can be found at : https://space.wh.sdu.edu.cn/info/1065/2075.htm