Astronauts on a future mission to Mars may not make it all the way to the Red Planet and back without experiencing kidney failure, new research has found.
While not usually considered one of the main dangers of space travel, a journey as far as Mars could alter the structure and function of astronauts' kidneys, leading to permanent damage, according to a new paper in the journal Nature Communications.
This damage would result from cosmic radiation from the rest of the galaxy—known as Galactic Cosmic Radiation (GCR)—which are high-energy particles that are usually absorbed by the Earth's magnetic field, protecting us on the ground and partially shielding the astronauts in low-Earth orbit.
However, on the long two-year round trip to Mars and back, an astronaut would be exposed to a large amount of GCR, damaging their organs and DNA.
"If we don't develop new ways to protect the kidneys, I'd say that while an astronaut could make it to Mars they might need dialysis on the way back. We know that the kidneys are late to show signs of radiation damage; by the time this becomes apparent, it's probably too late to prevent failure, which would be catastrophic for the mission's chances of success," study co-author Keith Siew, a researcher at University College London's (UCL) Department of Renal Medicine, said in a statement.
We have long known that space travel can lead to myriad health issues for astronauts, ranging from bone mass loss to kidney stone development, but only a very small proportion of astronauts—those who traveled to the moon—have been exposed to the full force of GCR, and this was for fewer than two weeks. This means that we haven't had much of an idea of what impacts GCR will have on the human body—until now.
In the paper, the researchers describe how they analyzed samples from humans and mice from over 40 low-Earth missions, and experimentally tested the effects of a Mars mission equivalent dose of GCR on mice and rats.
They discovered that the kidneys of both mice and humans are "remodeled" by space conditions, which caused changes to the way the kidneys process salts and an increased likelihood of kidney stones. These may be due to the effects of microgravity, however, or perhaps due to a combination of GCR and microgravity.
The researchers also found that the kidneys of mice exposed to conditions equivalent to a two-and-a-half-year trip to Mars were permanently damaged.
"We know what has happened to astronauts on the relatively short space missions conducted so far, in terms of an increase in health issues such as kidney stones. What we don't know is why these issues occur, nor what is going to happen to astronauts on longer flights such as the proposed mission to Mars," Siew said.
The researchers stress that this issue needs to be seriously considered before we send astronauts to Mars.
"Our study highlights the fact that if you're planning a space mission, kidneys really matter. You can't protect them from galactic radiation using shielding, but as we learn more about renal biology it may be possible to develop technological or pharmaceutical measures to facilitate extended space travel," study author Stephen B. Walsh, a professor at UCL's Department of Renal Medicine, said in the statement.
"Any drugs developed for astronauts may also be beneficial here on Earth; for example by enabling cancer patients' kidneys to tolerate higher doses of radiotherapy, the kidneys being one of the limiting factors in this regard."
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