Researchers have uncovered unexpected dangers for those brave enough to fly into space.
Astronauts on the Apollo missions to the moon have been found to have much higher rates of cardiovascular disease, with the likely cause being radiation from deep space.
In the first study of its kind, researchers from Florida State University examined the higher than expected rate of cardiovascular disease in astronauts who had travelled to the moon.
Apollo crew members heading to the moon would have been away from the protective influence of the Earth.
As a result, they were exposed to higher levels of “cosmic radiation” than anyone else in the astronaut corps, the researchers write in the journal Scientific Reports.
Of the 24 astronauts who flew on the Apollo lunar missions, eight have died, half of them from cardiovascular problems.
That is four to five times higher than the rate among non-flight astronauts or those who only travelled in low Earth orbit.
"We know very little about the effects of deep space radiation on human health, particularly on the cardiovascular system," said Prof Michael Delp, dean of the college of human sciences at the university.
“This gives us the first glimpse into its adverse effects on humans.”
To test whether radiation was behind the high rates of cardiovascular disease, the research team exposed mice to the same type and level of radiation the astronauts experienced.
After six months, the mice showed the kind of blood vessel damage that leads to the hardening of the arteries in humans.
The mouse data thus showed that “deep space radiation is harmful to vascular health”, Prof Delp said.
The team believes the radiation damages the sensitive cells that line the blood vessels.
Criticisim
However, an Irish expert in space radiation has said the study goes against current findings.
Emeritus professor Denis O’Sullivan, of the Dublin Institute for Advanced Studies, questions the link between the radiation and later health outcomes.
He has studied radiation doses to astronauts and to airline flight crew for decades, working on several Apollo flights and for the European Space Agency.
“It sounds like very bad news for human space travel if it is true,” he said.
However, he noted that crew on the International Space Station receive higher radiation doses than astronauts who reached the moon.
“[The study] would go against what most people would think. There may be biomedical conditions here that have nothing to do with radiation,” he said.
Prof Delp's findings come as the US, Russia, China and Europe make plans for deep space missions to the moon and to Mars.
Prof Delp is working with the US National Aeronautics and Space Administration to conduct further studies on the 16 surviving Apollo astronauts and their vascular health.
