There’s no question about it: astronauts are privileged to be able to travel into space, with the realities of their out-of-this world journey beyond most people’s imagination.

But while the views are spectacular and most astronauts cherish every minute of their journey, when they touch back down on Earth they have to undergo a rehabilitation process to rebuild their muscle mass and get their bodies used to life on Earth once more.

That’s because of the immensely difficult conditions that the body has to endure in space – something that we’re still learning about to this day.

And a recent study by researchers at University of California San Diego has demonstrated just how much stress each cell in a person’s body is under during space travel.

In the paper, which was recently published in the journal Cell Stem Cell, the research team tracked changes to stem cells on board the International Space Station, after having a small box containing the cells delivered to the ISS via a SpaceX resupply mission.

The stem cells were contained in a purpose-built ‘nanobioreactor’, an AI-powered platform that allowed the stem cells to be cultured and monitored while they were in space.

And the results were astounding. Not only did the cells age much quicker than they would on Earth, the AI imaging was able to capture the cells working much faster than they would on Earth, with their rapid changes meaning that they weren’t able to rest, recover, and regenerate as we would usually expect.

Moreover, damage to the cells was evident, with inflammation and stress alongside the reduced ability to regenerate healthy new cells suggesting that, if they were inside a human body, that person would be more disease-prone, would visibly age faster, with a reduced immune system too.

Incredibly, this all happened in under 45 days, proving just how damaging space travel can be on the human body, as UC San Diego’s Catriona Jamieson explained in a statement:

“Space is the ultimate stress test for the human body. These findings are critically important because they show that the stressors of space — like microgravity and cosmic galactic radiation — can accelerate the molecular aging of blood stem cells. Understanding these changes not only informs how we protect astronauts during long-duration missions but also helps us model human aging and diseases like cancer here on Earth. This is essential knowledge as we enter a new era of commercial space travel and research in low earth orbit.”

This might all make for bleak reading, especially for those for whom ‘space travel’ is a bucket-list staple. But there is good news.

The researchers found that in a healthy environment the cells did begin to recover, with some of the damage reversing over time. So with proper care and rehabilitation, not all the damage caused by this once-in-a-lifetime adventure needs to be permanent.

If you think that’s impressive, check out this story about a “goldmine” of lithium that was found in the U.S. that could completely change the EV battery game.