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A 2016 study reached a shocking conclusion for those who dream of space travel: going to the moon might cost you your heart.
Researchers wrote in Scientific Reports that 43 per cent of the Apollo astronauts who travelled beyond Earth’s protective magnetic field, exposing themselves to the harsh radiation of deep space, had died of cardiovascular disease.
For astronauts who went only to low-Earth orbit and didn’t fully leave the “magnetosphere”, the rate of death from heart disease was 11 per cent.
The authors concluded astronauts who went to the moon were four to five times more likely to die from heart disease. This risk calculation was heavily disputed, with an obvious limitation being the tiny sample size of Apollo astronauts who had died at the time (seven).
Follow-up papers argued the risk assessment was skewed because researchers didn’t properly account for risk factors such as age, and the fact one of the astronauts had existing heart issues separate to his exposure to deep space.
Nevertheless, the research focused attention on an indisputable problem: the radiation-lashed, zero-gravity wilderness of space exerts dangerous pressure on our soft, Earth-adapted mammalian bodies.
The Apollo astronauts and the recent Artemis II lunar visitors were only beyond the Earth’s magnetosphere for a matter of days.
As the ambitions of Elon Musk, the Australian Space Agency and NASA shift to long-term lunar habitation and travel to Mars, knowing whether the body can cope with months-long deep-space missions has never been more critical.
One of Australia’s leading cardiologists, having investigated just that issue, found the effects of such missions could be catastrophic.
Reproducing galactic rays
“An enormous amount of effort and money and resources has gone into developing the hardware and rocketry to get humans into space, whether it’s SpaceX, Blue Origin, or NASA’s Artemis missions,” says Professor Jason Kovacic, chief executive of Sydney’s Victor Chang Cardiac Research Institute and life-long space nerd.
“Far, far less attention has been paid to the human body and what that’s going to have to endure.”
Put another way: what’s the point of billion-dollar rockets if all the crew are toast?
‘Galactic cosmic rays tear straight through the side of spaceships.’
Professor Jason Kovacic
With collaborators at the Icahn School of Medicine at Mount Sinai in New York, Kovacic co-led new research in Clinical and Translational Medicine scrutinising how our hearts might fare on a long-term mission to the moon or Mars.
Space radiation, he says, emanates from stars and blasts from supernovae that have strewn the universe with a deadly web of galactic gamma rays.
Earth’s stewing molten core thrusts out a magnetic field that shields us from this cosmic lashing. Only 28 people have travelled beyond it (24 Apollo astronauts and four from Artemis earlier this year).
Spacecraft provide only partial protection from the radiation. “Galactic cosmic rays tear straight through the side of spaceships,” Kovacic says.
“It is possible to shield from it, but it requires very thick lead, and putting that kind of quantity of lead in a spaceship makes it too heavy to actually put in space.”
Previous studies have replicated space radiation using a single-ion beam generated using one element. Real space radiation is much more complex and high-energy, stemming from a raft of elements including hydrogen, helium, iron and uranium.
To better replicate long-term exposure to space radiation, the researchers used NASA’s Space Radiation Laboratory on Long Island, which replicates the radiation from a range of those elements in space. Some mice were exposed to the radiation.
“That was very carefully crafted by the NASA engineers to represent a physically and biologically relevant exposure that would realistically mimic long-duration deep space missions,” Kovacic says.
Key artery lining ‘obliterated’
Kovacic scrutinised the hearts of the mice more than a year later. A key protective lining of their arteries had been “obliterated”.
“The profound findings are that after we irradiated these mice and watched them for 16 months, the endothelium, which is the lining cells of the blood vessels, was basically stripped bare in the arteries.”
Mice are more resilient to clotting than humans, he says. If we lost this protective lining, clots would probably form quickly in our arteries and vessels.
“At the extent we saw the endothelium stripped, that would cause widespread clotting, which would likely be fatal.”
The small pilot study had a tiny sample size of less than a dozen mice. “We don’t know how transferable [the results] are [to astronauts],” Kovacic says, adding the research needs to be repeated and expanded.
“But if something like this were to happen in humans, it would be catastrophic. And the stakes are high. It’s not like one person may be affected and the rest of the crew won’t. It’s likely that the whole crew would be affected.”
The radiation had also increased and destabilised artery-clogging plaque, casting serious doubt on whether the human body could really sustain long-term space travel without serious leaps forward in cosmic exploration technology and spacecraft design.
As the Space Race 2.0 accelerates, space agencies are investigating radiation-repelling shelter designs. Lunar colonies may have to live underground.
Meanwhile, researchers this week reported the test results of a 26-kilogram protective space vest. The “AstroRad” vest was strapped to a dummy and sent around the moon during the uncrewed Artemis I mission; radiation monitors showed it could reduce the radiation dose of severe solar storms by 40 to 60 per cent.
The Artemis II crew also ferried vials of their own bone marrow to the moon and back to see how the cells warped in space, possibly giving us new insights into cancer treatments.
Says Kovacic: “We’ve got a lot of work to do to really understand the effects of longer duration space missions into deep space before we go blasting off to Mars.”
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Angus Dalton is the science reporter for The Sydney Morning Herald.Connect via X or email.From our partners
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