Travelling to Mars may speed up the ageing process – making it dangerous to send humans to the Red Planet, scientists fear. 

Many space agencies, including Nasa, have embarked on plans to put humans on Mars, with SpaceX planning to launch the first manned flights as early as 2026.

However scientists at the world-renowned Mayo Clinic hope to prevent such trips from triggering a lethal ageing process known as cell senescence, and in February will start the first-ever study into the phenomena in astronauts.

The team will be taking blood and urine samples from four members of the first all-civilian crew to fly to the International Space Station (ISS), to see if they can spot early signs of senescence. 

The ISS lies within the protective magnetic bubble known as the Van Allen belt, which shields the Earth from radiation and the crew will be there for only 10 days. 

However travellers to Mars would have no such protection, and would be subjected to the conditions for months or years. Previous studies have found that astronauts who flew lunar missions were five times more likely to die from cardiovascular disease than those who went into low orbit.

Dr James Kirkland, an expert on cellular ageing at Mayo, said: “This flight will give us an idea of whether routine spaceflight, without even going beyond the Van Allen belt, is associated with cell senescence. 

“If we see senescence even under these conditions, we would certainly want to do some work in preparation for a longer mission. Something will have to be worked out before or longer before interplanetary flights are really feasible.”

‘Zombie cells ‘

As humans age, cells in the body increasingly enter the state of permanent torpor known as senescence.  Neither alive nor dead, these ‘zombie cells’ prevent the body from replacing the non-functioning cells but they also are not cleared away. 

Instead they can pump out chemicals that increase inflammation in the body, ramping up the risk of disease. In youth, senescent cells are important, clustering around the site of injuries as a signal to the immune system that there is damage that needs repairing. 

Without them, wounds heal much more slowly. In those younger years, the zombie cells are cleared away afterwards, but as people age, the immune system loses the ability to sweep them away.

“You find senescence in conditions where cells are under stress, and they deform,” added Dr Kirkland.

“Zero gravity results in changes in cell shape, and the high G-force when a rocket takes off could also conceivably contribute to DNA cellular senescence.  

“Then there is radiation. The crew on the ISS will be inside the Van Allen belt but the real worry is what’s going to happen if there is a Mars mission, and if there is a solar flare, because then you’re dealing with atomic radiation. 

“We’ve found in preliminary studies very low doses of atomic radiation can drive a cell into senescence at much lower levels than x-rays or gamma rays.

“And, with atomic radiation, it could pass right through the spacecraft: it’s hard to stop. So if there’s a Mars mission this could really be a major problem.

“I’m a physician, not a space scientist, so my view is biased, but I’d say the health problem is pretty darn bad, and I’m very worried after what I’ve seen.”