Madness and vision loss: Doctors reveal what astronauts can expect on their journey to Mars.

Approximately 70% of astronauts face significant vision issues after extended missions aboard the ISS, according to a new study. To develop these problems, one must spend over six months in orbit. This poses a threat to missions to the Moon and Mars.

The precise diagnosis, as stated by ophthalmologist Santiago Costantino from the University of Montreal, is known as spaceflight-associated neuro-ocular syndrome (SANS). Research indicates a one-third reduction in eye stiffness (meaning the retina becomes loose), a slight increase in intraocular pressure, along with changes in other parameters. Patients experience this as a narrowing of the visual field, and in severe cases, swelling of the optic nerve may occur.

The underlying causes relate to microgravity. Blood continuously flows to the eye as if a person were hanging upside down. Additionally, the typical "pulse" creates a sort of hydraulic shock in the soft ocular tissues.

For now, it seems premature to sound the alarm. In most cases, these issues can be addressed with corrective eyewear. However, what will happen when a mission to Mars is launched?

Researchers are concerned not only about the stay on the Red Planet but also about the lengthy journey. The flight could last from one to two years, with all that time spent in radiation and microgravity. Moreover, upon arrival, no adequate medical assistance will be available as on Earth, and Martian gravity, which is significantly weaker than ours, is unlikely to restore the body to a normal state.

In addition to gravity, the danger of long flights far from our planet lies in radiation. A constant stream of radiation particles comes from the Sun, while more intense radiation emanates from interplanetary space. On Earth, as well as on ISS crews, we are protected because the magnetic field prevents particles from penetrating deeply. These particles seem to "screw" onto the lines of Earth's magnetic field and safely "discharge" above the magnetic poles during auroras. But beyond approximately 10,000 kilometers, radiation becomes a severe threat. There will be no escaping behind some shelters or walls.

Beyond the obvious (radiation sickness), medical experts believe radiation exposure will impair cognitive abilities. Astronauts may simply go insane. The first settlers will face particularly tough challenges. Mars cannot shield against radiation as effectively as Earth. They will need to hide deep underground, but such stations still need to be constructed. This is particularly challenging for the first generation of settlers. They will not have it easy.

To lift spirits, Elon Musk's company sent space tourists, led by billionaire Jared Isaacman (who is being considered for the head of NASA for this feat), directly into the Van Allen belts, where Earth "stores" radiation. They reached an altitude of 1,400 kilometers. Right into the heart of radiation. And yet, nothing happened (though one mission participant later complained about health issues)! It is clear that nothing will happen: a brief visit to radiation zones will not cause harm. This is not a long-duration flight.

Overall, astronauts are reporting health problems more frequently than in heroic times. Long-duration flights have been practiced since the 1970s. Likely, this is a result of softened selection criteria. Today, "just healthy" individuals are sent to orbit. In the aforementioned "eye" study, the average age of participants was 48, with a third being women. It is evident that in the hypothetical year of 1970, not all of them would have passed the medical examination. However, Mars is also planned to be explored not by iron heroes but by ordinary people.