Deep Space Radiation Could Cause Learning and Memory Problems, Making Astronauts Unable to Deal with Unexpected Situations: Study

Sending humans to Mars could leave astronauts with neurological problems, according scientists who studied mice in conditions which they claimed replicate deep space. The authors of the paper published in the journal eNeuro exposed mice to what they described as a low dose of radiation of neutrons and photons over a six month period. They set the amount at 18 Centigrays (the unit used to measure the dose of radiation absorbed) with a rate of 1 mGy/day over the course of the study. This appeared to change how the neurons in their hippocampus (which deals largely with memory) worked; and fiddled with nerve impulses on pathways in the hippocampus and cortex. What's more, behavioral tests showed the mice were left with learning and memory problems, and appeared more distressed and anxious. The team argued the "spectrum of behavioral deficits" they saw in the mice "would clearly impair the abilities of astronauts needing to respond quickly, appropriately and efficiently to unexpected situations that arise over the course of a mission to Mars."

The team explained it was previously difficult to replicate and study the effects of radiation in deep space, but said they were able to use a new neutron irradiation facility which they claimed simulated the realistic low dose rates found in deep space. However, the authors were optimistic the risks wouldn't halt any plans for humans to visit Mars. "In the long term, the nature of the radiation environment in space will not deter our efforts to travel to Mars, but it may be the single biggest obstacle humankind must resolve to travel beyond the Earth's orbit," they wrote. However, Professor Francis A. Cucinotta of the University of Nevada, Las Vegas, Department of Health Physics and Diagnostic Sciences, who did not work on the new study, was skeptical of the findings and argued they could be "misleading." Cucinotta told Newsweek the radiation used was not reflective of the neutrons which occur in space, and the dose exceeded NASA's exposure limits 9-fold for females and 4-fold for older males. "There is no way an astronaut would be exposed to this neutron energy source or the equivalent dose used. It would violate NASA and other space agencies' dose limits," he said. Cucinotta also questioned why the authors used a strain of mice known to be sensitive to cognitive changes. Getting to the red planet involves traveling for two years in an environment with high levels of radiation. ESA Director General Jan Wörner recently commented: "So far, we have no spacecraft where humans within would survive that."