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Goodbye space: astronauts lose too many red blood cells

Created on 30 August, 2023Nature Scence • 221 views • 2 minutes read

The race to the Moon and Mars has begun

The race towards the Moon and Mars has begun, but a study published in Nature Medicine seems destined to change the much talked about projects: scientists have discovered that the human organism is not made to travel in space. In fact, a long stay in Earth's orbit is enough to significantly reduce the number of red blood cells present in the blood, and without red blood cells you can't go anywhere.

The research involved 14 astronauts on a mission to the Space Station for six months, who were asked to exhale at regular intervals into containers, which were then sealed and brought back to Earth for analysis. The scientists then verified the amount of carbon monoxide in the astronauts' breath, measuring by analogy the amount of red blood cells that "die" when air is expelled from the lungs.


Red blood cells carry oxygen from the lungs to the body's tissues and carry some of the carbon dioxide from the tissues back to the lungs to be eliminated with breathing. As they do this work they age and eventually die, replaced by more red blood cells that are produced by the bone marrow.

By examining the carbon dioxide of astronauts, the researchers found that the amount of erythrocytes that become inactive when a human being is in space is 52% higher than on Earth. Not only that, the state of anemia caused by staying in orbit persists even after the return of the astronauts, with individuals who have suffered from it for years.

Excessive hemolysis, this is the technical term for the destruction of red blood cells, can cause fatigue, shortness of breath and tachycardia, all conditions that are unsuitable for a long and demanding journey such as the one necessary to reach Mars. Normally, every day we lose 1-2% of the red blood cells in the blood, which are rapidly replaced. But in astronauts the replacement process fails to cope with the losses, generating significant anemia conditions.

Other studies will be done, because the reason for the excessive disappearance of red blood cells when one remains in orbit for a long time is not yet clear, but this problem is only one of many that astronauts will have to face on a trip to Mars, which the billionaire Elon Musk optimistically expects to deliver within a few years. In space, muscle mass and bone mass decrease, generating osteoporosis phenomena. Liquids concentrate in the upper part of the body, swelling the neck and head, cognitive capacity decreases, eye movements become more tiring.

If all this were not enough, then there is the problem of cosmic radiation from which, on Earth, the planet's magnetic field protects us. Every year in Italy we undergo the equivalent of 11 chest x-rays equivalent to 3.3 millisieverts, the unit of measurement that quantifies them. Those who go to Mars, in the three years of travel, will receive about 1,200 mSv: upon arrival, the bold astronauts who will have to found the first colony will be exhausted, anemic, almost devoid of muscles and practically radioactive. Better perhaps to continue sending only robots.