National Geographic : 2016 Nov
Russian cosmonaut Sergey Volkov undergoes a battery of physical tests at Star City after returning from six months on the Interna- tional Space Station. Long stays in space—a trip to Mars might take seven months each way—can affect the body profoundly. COSMIC RAYS AND BRAINS Astronauts leaving Earth’s protective magnetic field would be vulnerable to fast-moving particles called cosmic rays. Compared with a healthy mouse brain (top), a mouse hit by “space-relevant” radiation (bottom) has fewer nerve-cell branches (green) and connec- tions (red) in its prefrontal cortex. Such mice explore less and have worse spatial memory—“a cause for concern” for Mars explorers, says Charles Limoli of the University of California, Irvine.