Britannica Sources used in this answer

Why are astronauts outside Earth’s magnetosphere at risk during large solar particle storms?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Space weather Earth's full North Polar auroral oval, in an image taken in ultraviolet light by the U.S. Polar spacecraft over northern Canada, April 6, 1996. In the colour-coded image, which simultaneously shows dayside and nightside auroral activity, the most intense levels of activity are red, and the lowest levels are blue. Polar, launched in February 1996, was designed to further scientists' understanding of how plasma energy contained in the solar wind interacts with Earth's magnetosphere.

Astronauts outside Earth’s magnetosphere are at significant risk during large solar particle storms because they lose the natural protection provided by our planet’s geomagnetic field.12

When astronauts are in low Earth orbit, the magnetosphere acts as a shield, deflecting the solar wind and trapping many harmful charged particles. However, during major solar events—such as solar flares and coronal mass ejections—the Sun releases intense bursts of energetic particles, primarily protons.1324

Outside the magnetosphere, in interplanetary space or on the surface of the Moon or Mars, there is no such barrier to block this radiation. Exposure to these high-energy particles can cause severe radiation injury, including damage to DNA and cells, radiation sickness, and an increased risk of fatal tumors. Because these storms are difficult to predict and the radiation is lethal, protecting human life during long-duration space missions remains a critical challenge for space exploration.15