Space, the final frontier, is an environment so inhospitable and vast that it could only be compared to traversing the world's oceans during the Age of Sail. While sailors struggled to fight scurvy two centuries ago, astronauts today now face the threat of damage at the cellular level.
A scientific report released in October concluded that long-duration spaceflight causes mitochondrial damage producing something similar to accelerated aging. For those of you who fell asleep in science class, mitochondria generate the power for organic cells. If mitochondria stop functioning, we'll gradually start dying.
The report produced by the Guy Foundation, an independent British research foundation, cited multiple causes behind the cellular damage. First is the increased radiation in space, which was already known to cause an increased risk of astronauts developing cancer later in life. Zero gravity also removed the stimulus needed to maintain healthy mitochondria. While residents on the International Space Station exercise constantly to stave off muscle and bone loss, there's no workout to help your cells.
Earth's magnetic field also keeps mitochondria stable. The lack of similar fields in outer space, the Moon and Mars could hamper permanent settlement in the future. It won't be a permanent barrier, but an obstacle that space agencies will have to tackle as they explore the great unknown.
The report did mention that there isn't much data on long-term health outcomes because not that many people have spent months in space. However, as private space companies ramp up operations alongside the effort to return to the Moon, there will be more people than ever inhabiting the final frontier and an increased need for long-term health data.
Humanity is quickly finding out how hostile space is to life. A study into SpaceX's 2021 Inspiration4 mission found four private astronauts suffered a modest decline in cognitive function. The mission was less than three days longer. However, data from the same mission found that women can recover more quickly than men. While agencies are attempting to dry-run long-term space missions on Earth, like NASA's year-long Mars mission simulation, there's no way to recreate every variable that astronauts will face.