Astronauts can survive a trip to Mars, but one critical internal organ will likely fail

Space journeys that stretch far beyond home are on the horizon. Crews heading for Mars will face conditions quite different from those on Earth, and researchers have been working to figure out what might happen to the human body during these extended voyages.

Kidneys have been a big question mark. Recent work reveals that these important organs could face more trouble than previously assumed, including a higher risk of stones and lasting damage.

Several studies have hinted at health concerns for astronauts ever since humans first ventured outside Earth’s protective zone, but the new findings shed light on why such problems arise in the kidneys.

Dr. Keith Siew from the London Tubular Centre, based at the UCL Department of Renal Medicine, and his colleagues have pieced together a detailed picture of what happens when living beings – human and otherwise – experience space-like conditions for weeks to years.

Space missions and human kidneys

The latest study was conducted under a UCL-led initiative involving over 40 institutions on five continents.

The team considered data from 20 different research cohorts and samples linked to over 40 Low Earth orbit missions to the International Space Station, plus 11 simulations with mice and rats.

The work is described as the largest analysis of kidney health in spaceflight so far and includes the first health dataset for commercial astronauts.

It also involved seven simulations in which mice were exposed to radiation that mimicked up to 2.5 years of cosmic travel beyond Earth’s magnetic field.

Findings revealed that the structure and function of the kidneys are altered by spaceflight, with galactic radiation causing permanent damage that would jeopardize any long-distance mission.

Kidneys and deep space radiation

Astronauts in Low Earth orbit still benefit from partial shielding by our planet’s magnetic field.

Only 24 people – the ones who went to the moon – have been exposed to the full brunt of Galactic Cosmic Radiation for short trips of about 6-12 days.

Nobody has ventured on a years-long mission beyond the Earth’s magnetic boundary, so it was unclear how organs might hold up under more extreme conditions.

As part of the new study, researchers found that certain kidney tubules, which control delicate balances of salts and calcium, shrink after just a month in microgravity.

The kidneys also process salts in a way that increases the likelihood of kidney stone formation.

This new insight shifts the focus away from an older assumption that stones in space result mainly from bone loss causing elevated calcium in urine.

Longer distance, more radiation

The research highlighted that cosmic radiation cannot be fully blocked by typical shielding. When mice were given doses of simulated Galactic Cosmic Radiation equal to a mission length of up to 2.5 years, the animals showed irreversible kidney damage.

Some of the key observations point to changes in how the kidneys manage vital minerals, which impacts long-term health during space travel.

“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,” explained Dr. Siew.

“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.”

If scientists don’t develop new ways to protect the kidneys, any astronaut that makes it to Mars will likely need dialysis on the way home or upon arrival.

“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,” Dr. Siew concluded.

Human kidneys and future space travel

Space agencies have been aware since the 1970s that journeys outside our planet’s natural defenses lead to health concerns involving bones, eyes, and the cardiovascular system.

This new work puts fresh focus on the kidneys. It also highlights the importance of managing both microgravity and radiation, especially with more ambitious missions on the table.

“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,” noted Professor Stephen B. Walsh from the London Tubular Centre, UCL Department of Renal Medicine.

“But as we learn more about renal biology it may be possible to develop technological or pharmaceutical measures to facilitate extended space travel.”

Any drugs developed for astronauts may also be beneficial here on Earth. For instance, by enabling cancer patients’ kidneys to tolerate higher doses of radiotherapy, which is currently an impediment to that form of treatment.

What happens next?

Though this work only outlines organ changes up to two and a half years, it stands as the most comprehensive data currently available for that timescale.

Researchers say that pinpointing these risks is a vital first step before reliable solutions can be introduced.

The study’s international collaboration suggests momentum is building to safeguard astronauts’ kidneys, and future innovations could reach beyond space missions to help patients on Earth.

Experts note that learning how to handle the combined effects of microgravity and cosmic radiation will be key to making ambitious missions safer.

With evidence pointing to serious kidney challenges, careful planning will be needed to keep crews healthy on journeys that last far longer than any undertaken before.

The full study was published in the journal Nature Communications.

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