(CN) — Elon Musk has said he plans to send a manned space flight to Mars in 2029. The mission presents numerous technological hurdles. But there could be another challenge, one that even Musk hasn’t thought of: whether or not our bodies are capable of making the 170 million-mile journey.
Many of the 24 astronauts who made it to the moon came home with a number of adverse reactions, including loss of bone and muscle mass, and a weakening of the heart and eyesight. Their time in space also appeared to lead to a high rate of kidney stones. Some have theorized that these effects are caused by radiation, both from our sun and from deep space.
On Earth, we are shielded from much of this radiation by our planet’s magnetic field.
A team of researchers from more than 40 institutions across five continents has been studying the effects of space flight on the kidneys. In a paper published Tuesday in Nature Communications, the team concluded that both the structure and function of kidneys are permanently altered by space flight, with microgravity — that is, gravitational force less than what we’re used to experiencing here on the ground — the likely culprit.
The two dozen people who have traveled to the moon and back were in space for only about a week or two. A round trip to Mars takes closer to two years.
“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,” said Keith Siew, the lead author of the paper and a research fellow at University College London, in a written statement. “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.”
Siew and his team studied data and samples from more than 40 low-Earth-orbit space missions involving both humans and mice, most of which went to the International Space Station, which orbits our planet some 250 miles above our heads.
They also studied 11 space simulations involving mice and rats, which were given doses of microgravity and cosmic radiation, equivalent to what they’d experience in 1.5 to 2.5 years in space, beyond Earth’s orbit. The authors claim their study is the largest ever “look at the effect of spaceflight on kidney function.” The results, they say, indicate that both human and animal kidneys are permanently “remodeled” by conditions in space.
Kidneys contain millions of tiny tubes, called renal tubules, that carry nutrients and other substances that the kidney has filtered back into the bloodstream. According to the study, some specific tubules, which are responsible for delivering calcium and sodium, show signs of shrinkage after just one month in space.
The scientists say that this tubular shrinkage is likely an effect not of cosmic radiation but microgravity — though they may have a combined effect, and more research is likely needed.
“Our data robustly and orthogonally supports tubular remodelling occurring in microgravity with and without [galactic cosmic radiation],” the authors write in their paper. “This is highly likely to have functional consequences, as tubular remodelling does in other scenarios.”
The fact that the altered kidneys process salt in a different way, the authors write, may be way they develop kidney stones at a higher rate.
Mice kidneys exposed to 2.5 years of cosmic radiation experienced permanent “damage and dysfunction,” according to the paper.
Another author of the study, Professor Stephen Walsh, also based at the University College London, explained the potentially implication of the findings in a written statement.
“If you’re planning a space mission, kidneys really matter,” he said. “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.”