The vacuum of space is filled with dangerous radiation that can seep through spacecraft, spacesuits, and even the bodies of astronauts, and scientists are trying to figure out the risks it poses for humans travelling beyond Earth’s protective atmosphere.
So if we ever want to send humans to Mars, scientists need to know what would happen to us if we get hit with radiation from a cosmic ray or a solar flare.
To get some insight, scientists exposed mice brains to radiation blasts designed to mimic a cosmic ray in a new study published May 1 in the journal Science Advances. Results showed that the mice experienced major brain inflammation that interrupted the ability of their neurons to communicate with each other. That seriously messed up the mice’s cognitive function and affected their ability to both learn and remember.
“This is not positive news for astronauts deployed on a two- to three-year round trip to Mars,” Charles Limoli, lead study author and professor of oncology, said in a press release.
We don’t know that much about what radiation does to astronauts because the International Space Station (ISS) hovers within the planet’s magnetosphere that protects against most dangerous space radiation. Still, even ISS astronauts are required to wear dosimeters that measure how much radiation they’re exposed to, and once they reach a certain limit, NASA will not allow them into space again.
A mission to Mars holds many more risks than just hanging out on the (ISS).
While travelling to the red planet, humans will have to fly straight through the radiation-filled remnants of billions of star explosions and through the dangerous streams of solar flares constantly erupting from the sun. So it’s critical that NASA and other space agencies understand how space radiation can affect human health.
Obviously we can’t expose human brains to radiation, but studying how it affects the brains of mice can give us some insight into how it might affect us.
Researchers took an initial brain scan of a group of mice and then hit them with a stream of ionized oxygen and titanium that mimics the type and intensity of radiation we’d encounter in space. Six weeks later they scanned the brains of the mice again and found some serious changes.
The mice had far fewer dendritic synapses — the branch-shaped structures on neurons that carry signals from neuron to neuron. Here you can see the dendrites before the radiation (left) and after the radiation (right):
The stream of radiation acted like a spray of bullets and broke off pieces of the dendrite branches.
The researchers then put the radiation-exposed mice and a group of radiation-free mice through a series of tests designed to measure learning ability and memory. The radiated mice were less curious and less interested in the learning tests than the normal mice and they were more easily confused on the memory tests.
What this means for space travel
If something similar happens to the brains of humans, that could significantly influence an astronaut’s ability to react to an emergency in space or concentrate on high-stress tasks, the authors conclude.
“Although we cannot simulate exactly the complex and prolonged charged particle irradiation pattern encountered in space, the present data do demonstrate that there is some likelihood of developing certain radiation-induced cognitive deficits,” they write in the paper.
Other research has shown that loss of dendritic branches is linked to cognitive diseases like Alzheimer’s. Similar but more severe results have been observed in brain cancer patients who get much higher doses of radiation in cancer treatments.
It would likely take months for any kind of brain impairment to show up in astronauts if they were hit with a high-intensity beam of radiation, Limoli said. But that’s plenty of time for damage to set in during a mission to Mars, which would take at least six months using on today’s space travel technology.
Solutions for long-term space travel could include outfitting spacecraft with areas that can shield against radiation better, but there’s really no way to completely avoid exposure, according to Limoli.
Right now Limoli is working on treatments that can protect against neuron damage, but the research is still in its infancy.
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