What will happen to the brain of an astronaut during a mission to Mars? Nothing good. It will be precipitated by destructive particles that could permanently impair cognitive function, according to a radiation oncology study from the University of California, Irvine.
Charles Limoli and his colleagues found that exposure to high-energy charged particles - such as the galactic cosmic rays that bombard astronauts during long space flights - cause significant damage to the central nervous system and lead to cognitive impairment.
“Not the best news for astronauts preparing for a two- or three-year voyage to Mars,” says Limoli, professor of radiation oncology at Caltech School of Medicine in Irvine. - Decreased productivity, memory deficits, decreased concentration and attention during space flight can affect mission-critical activities; exposure to these particles can also lead to long-term cognitive impairment throughout life."
As part of the study, scientists irradiated rodents (fully ionized oxygen and titanium) with charged particles at NASA's Space Radiation Laboratory at Brookhaven National Laboratory, and then sent them to the Limoli laboratory.
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Scientists have found that exposure to these particles leads to brain inflammation, disrupting signaling between neurons. The images showed how exactly the communication network of the brain is disrupted by contractions in the structures of nerve cells, for example, dendrites.
Additional synaptic changes, combined with structural changes, interfered with the ability of nerve cells to efficiently transmit electrochemical signals. Moreover, this led to a concurrent performance degradation when performing behavioral tasks designed to test learning and memory.
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These types of more serious cognitive impairments are common in brain cancer patients who receive high doses of photon radiation during treatment. In another study, Limoli is looking at the effects of chemotherapy and head radiation on cognitive function.
While the cognitive deficit will only show up in astronauts months later, Limoli says, the time it takes to fly to Mars will be long enough for the deficit to develop. People who work for extended periods on the International Space Station do not face the same level of galactic cosmic ray bombardment as they are still within Earth's protective magnetosphere.
The radiation particles that make up these galactic cosmic rays are mostly supernova remnants.
Limoli's work is part of the NASA Human Research Program. Exploring how cosmic radiation affects astronauts and exploring ways to mitigate these effects is critical to further human space exploration, as these risks will primarily manifest on missions to Mars and beyond the Red Planet.
What can we do to protect astronauts flying to Mars?
As a partial solution, Limoli says, the spacecraft should be designed with highly protected areas in which to rest and sleep. However, the high-energy particles will pass through the ship anyway, and there is no real way to avoid them.
Preventive procedures offer some hope. “We are working on pharmacological strategies that include components that will bind free radicals and protect neurotransmission,” says Limoli. "But the theory still needs to be optimized and refined."