Our interest in Mars has really taken off recently. The Red Planet has become a goal of human exploration – and settlement if you’re Elon Musk – because it’s the only planet in the solar system, other than Earth, where we know life may have existed.
There’s been plenty of research into how space travel affects the body. While many studies have looked at the effects of low Earth orbit (LEO) spaceflight, some have looked at the negative health effects associated with traveling beyond the Earth’s protective magnetic field, where it’s thought that exposure to galactic cosmic radiation (GCR) and weightlessness or microgravity are contributing factors.
Now, in a study led by University College London (UCL), researchers have conducted a range of experiments and analyses, the largest to date, into how the kidneys respond to longer spaceflights, like the one that’ll get us to Mars.
“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,” said Dr Keith Siew, a research fellow in renal medicine at UCL and the study’s lead and co-corresponding author. “What we don’t know is why these issues occur, not what is going to happen to astronauts on longer flights such as the proposed mission to Mars.”
Kidneys are indispensable (read: life-sustaining). They remove waste products and balance the body’s fluids via the urine; they regulate acid, salts, and minerals such as sodium, calcium, potassium and phosphorus in the blood; they release hormones that regulate blood pressure; they produce an active form of vitamin D that promotes strong, healthy bones; and they control the production of red blood cells.
Only the 24 people that have traveled to the Moon have been exposed to unmitigated GCR, and only for a relatively short six to 12 days. So, the researchers looked at physiological, anatomical and biomolecular data from 20 study cohorts, including samples from over 40 LEO space missions undertaken by humans and mice – mostly to the International Space Station (ISS) – and 12 space simulations involving rats and mice. In seven simulations, mice were exposed to GCR doses equivalent to 1.5- and 2.5-year Mars missions, emulating deep space travel.
Structurally, both human and rodent kidneys appeared to be ‘remodeled’ by exposure to space conditions. After less than a month in space, the tubules that fine-tune calcium and salt balance showed signs of shrinkage, which the researchers say was likely due to microgravity rather than GCR. However, further research is needed to confirm this or whether, in fact, GCR contributes to these structural changes.
Previous studies have shown that astronauts have an unusually high rate of kidney stone formation, which has been attributed to microgravity causing bone loss that leads to a build-up of calcium in the urine. The present study indicated, though, that space flight fundamentally altered how the kidney processed salts, which likely contributed to the formation of kidney stones.
Most troubling, the kidneys of mice exposed to 2.5 years’ worth of GCR showed permanent kidney damage and loss of function.
“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,” Siew said. “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.”
This study represents the most comprehensive data to date on how up to 2.5 years of space travel affects the kidneys, which is relevant to any proposed trip to Mars. But, the researchers say, there’s still time to develop a fix.
“Our study highlights the fact that if you’re planning a space mission, kidneys really matter,” said Stephen B. Walsh, from the UCL Department of Renal Medicine and a co-corresponding author on the study. “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.”
The study was funded by the UK Space Agency, the Wellcome Trust, St Peters Trust, and Kidney Research UK (KRUK) and published in Nature Communications.
Source: UCL