During Scott Kelly's space year, the astronaut was relentlessly jagged by radiation – equivalent to 10 x-rays per day for more than 11 months from March 2015. The onset damaged Kelly's DNA, affecting his immune system and increasing his risk for cancer. And Kelly was aboard the International Space Station, whose orbit around the Earth is within the magnetic field that surrounds our planet and blocks the most damaging forms of radiation.
Astronauts traveling to Mars or other space destinations will leave Earth's shelter cocoon for months or years at a time. And a new NASA-funded study suggests that chronic radiation exposure can damage both the mind and body of astronauts ̵
That could be a big deal.
"The nature of the radiation environment in space will not stop us from traveling to Mars, but it could be the biggest obstacle humanity has to solve to travel beyond Earth orbit," the researchers wrote in their study published on August 5th in the journal ENeuro.
Dr. Munjal Acharya, a radio oncologist at the University of California, Irvine, and principal author of the study, said radiation exposure "affects cognitive function and behavior at the cellular level," adding that exposure could make it difficult for astronauts unforeseen events effectively respond to circumstances or stressful situations.
The study suggests that at least one in five astronauts sent to Mars would return with severe deficits in cognitive function.
For the study – the first to simulate the radiation that astronauts were exposed to on a mission to Mars – Acharya and his staff exposed 40 mice to radiation for six months and then tested the animals' memory and behavior.
One test found that mice exposed to radiation were less capable, others showed that the exposed mice were so concerned that they "froze" in situations where they did not. The control animals were not worried.
"This fear was so great that they were still frozen," Acharya said, adding that the radiation seemed to make it hard for the mice to learn and adapt by making connections between different regions of the world Brain of the animals weaken.
JD Polk, NASA's Chief of Health and Medicine, described the new study as an important contribution to understanding the potential risk to astronauts of radiation. However, he warned against excessive alarms and said the animals in the study had been exposed to higher levels of radiation than astronauts would likely have experienced in space.
"I do not expect doses we expect on a Mars mission Astronauts have a massive cognitive decline," said Polk, who is based at the space agency headquarters in Washington. "Is there a high risk that they will return with a terrible cognitive decline and forget how to press the red button for reentry? No.
Charles Limoli, a radio oncologist who heads the NASA Specialized Center of Research at the University of California at Irvine and co-author of the new study, denied this assessment. "I am not sure which literature Dr. Polk reads, but I disagree with the context in which he puts our work – and I disagree with his statements," he said in an e-mail NASA is already working to limit the exposure of astronauts to future missions.
The agency is currently testing a radiation protection vest intended to limit astronaut radiation exposure, and its new Orion spacecraft will be equipped with a radiation measuring device that alerts astronauts to a rise in radiation – so the crew can enter the Center of the spaceship and shield yourself with bags full of supplies.
Orion is mainly used for missions to the moon, but could be used to transport astronauts to a moon-orbiting spaceport from which space carriers fly to Mars with a larger spacecraft called the Deep Space Transport could. Researchers at the Langley Research Center's agency in Hampton, Virginia, are currently working to help protect Asures, who could be used for the latter vehicle.
As hydrogen absorbs radiation, scientists are exploring ways to integrate hydrogen-rich materials into the spacecraft's structure. A contemplated possibility is to equip the walls with water tanks. Another option is to add a polyethylene shield – the same lightweight plastic used to make water bottles.
The disadvantage of adding water or plastic to the Deep Space Transport is that it makes the spaceship considerably heavier, Polk said. As a result, scientists are looking for other solutions, such as giving the vehicle its own radiation-blocking electromagnetic field – a complicated and potentially expensive technology that Polk compares to the deflector shields familiar to viewers of Star Trek.
Considering the Costs Considering the weight of radiation shielding, NASA is anxious to see how much shielding is needed to protect astronauts. Polk said future research, including additional studies on animals, could help NASA make that decision. Acharya said his team will conduct new studies to determine the exact mechanisms for cognitive decline, with the aim of finding ways to block it.
"I do not want anyone to get cancer while he's on Mars," said Polk. "I do not want anyone to have radiation issues while on Mars, I want to make sure he's protected."
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