Astronauts on future missions to Mars could succumb to severe cognitive impairments, including anxiety and a compromise of decision-making skills due to high levels of cosmic radiation, according to research published in Scientific Reports.
Scientists studied the effects of deep space cosmic radiation on rodents, and determined that a "Mars mission will result in an inevitable exposure to cosmic radiation that has been shown to cause cognitive impairments in rodent models, and possibly in astronauts engaged in deep space travel."
While astronauts on the International Space Station—who often spend months in space—suffer from negligible effects from cosmic rays because they are protected from the Earth's magnetosphere, deeper space missions would expose them to adverse effects, said the researchers. Even astronauts who travelled just outside of low Earth orbit to the Moon have suffered from negative effects of radiation. In July, a paper also published in Scientific Reports linked cardiovascular problems in Apollo-era astronauts to deep space radiation.
But the latest paper warns that cosmic radiation could greatly impact the ability of Mars astronauts to perform their job as they are pummeled with cosmic rays. "As NASA plans a mission to Mars, astronauts will inevitably be exposed to low fluences of highly energetic and fully ionized nuclei that define the spectrum of galactic cosmic rays," reads the study.
"A real and unique threat to the integrity of neural circuits in the brain."
The research, led by scientists from the Department of Radiation Oncology at University of California, Irvine, and the Department of Radiation Oncology at Eastern Virginia Medical School, tested the functional consequences of cosmic radiation exposure on the brains of mice over a period of 12 weeks. Behavioural tasks were given to the mice 12 and 24 weeks after the irradiation period, with the cosmic rays posing "a real and unique threat to the integrity of neural circuits in the brain."
Galactic cosmic rays are composed of high-energy charged particles that are deflected from Earth by the magnetosphere. They are so full of energy, in fact, that they can penetrate spacecraft hulls, then find their way into body tissue.
NASA is already investigating how to deal with the radiation that would be exposed to astronauts on a trip to the Red Planet. Solutions include special areas of a ship where astronauts could be protected from solar flares and cosmic rays, and even localized electric or magnetic protective fields that would generate a defensive bubble around a spacecraft.
"The radiation thing is often brought up, but I think it's not too big of a deal," said Musk, who suggested that although there may be an increased risk of cancer, colonists could protect themselves in the Interplanetary Transport System by gathering behind a column of water.
But the cosmic problems don't end on the spacecraft. Mars has no global magnetic field to deflect energetic particles, with its thin atmosphere only providing minimal protection to any habitats on the surface.
For now, researchers are trying to define the level of acceptable risk to radiation exposure, but warn that even though their study looked at radiation effects on rodents, there is "no data that suggest[s] the response of rodent neurons to cosmic radiation would differ in a fundamental way from those of humans."
"Thus, the most logical conclusion to draw from these studies is that cosmic radiation exposure poses a real and potentially detrimental neurocognitive risk for prolonged deep space travel."
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