It's no secret that NASA has taken on an overwhelming task: to send people to Mars by the 2030s. Why overwhelming? Because it is enough to understand that a typical trip there will take three to six months, and the crew will have to stay on the planet for up to two years before the alignment of the planets allows it to return home. This means that astronauts will have to live in reduced (micro) gravity conditions for at least three years - this significantly exceeds the current record for continuous stay in space set by Russian cosmonaut Valery Polyakov: 438 days.
In the early days of space travel, scientists worked hard to figure out how to overcome gravity so that a rocket could catapult into space and land people on the moon. Today, gravity also remains on the agenda of science, but this time we are more interested in how reduced gravity affects the health of astronauts, especially their brains. After all, we evolved to exist in Earth's gravity (1 g), not in the weightlessness of space (0 g) or the microgravity of Mars (0.3 g).
Brain in a vat
So how does the brain deal with microgravity? In short, very bad - however, information on this is limited. We know that astronauts' faces redden and swell in zero gravity - a phenomenon affectionately called the "Charlie Brown effect." This is largely because fluid, made up mainly of blood (cells and plasma) and cerebrospinal fluid, is displaced towards the head, causing faces to become puffy and round and legs to thin.
These fluid displacements are also associated with "space sickness" (similar to sea sickness), headaches and nausea. Recently, they have also been associated with blurred vision due to pressure build-up with increased blood flow; the brain itself floats up to the top of the skull, putting pressure on it. Despite the fact that NASA considers visual impairment and displacement of the brain to be the main risk to the health of any person on Mars, it has not yet been possible to find out what causes it, as well as how to prevent it.
Physiology and Biochemistry professor Damien Bailey of the University of South Wales believes that certain parts of the brain end up receiving too much blood because nitric oxide builds up in the bloodstream, an invisible molecule that usually floats there. The arteries that supply the brain with blood relax, so they open up more. As a result of this rise in blood flow, the blood-brain barrier - the “shock absorber” of the brain - becomes overloaded. Water builds up slowly, the brain swells, and the pressure increases.
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Imagine a river overflowing its banks. The most important thing in all this is that not enough oxygen is supplied to certain parts of the brain. This is a big problem that can explain blurred vision, as well as other effects that appear on the ability of astronauts to think, concentrate, reason and move.
A trip to the "vomit comet"
To test an idea, scientists must put it into practice. But instead of asking NASA to travel to the moon, they simply decided to break free of the earth's gravity by simulating weightlessness on a special plane called a vomit comet, a vomit comet.
Rising into the air and then descending, this aircraft performs up to 30 parabolic figures in a single flight to simulate the feeling of weightlessness. The free fall lasts only 30 seconds, but the face manages to swell in half a minute.
After securing all the equipment securely, the scientists took measurements among eight volunteers, each of whom made one flight every day for four days. They measured blood flow in various arteries that support the brain using portable Doppler ultrasound, which causes high-frequency sound waves to bounce off circulating red blood cells. They also measured the level of nitric oxide in blood samples taken from a vein in the forearm, as well as other invisible molecules, including free radicals and brain-specific proteins (which reflect structural damage to the brain), which could tell if the blood-brain barrier is forced open.
Initial findings confirmed exactly what was expected. Nitric oxide levels increased after repeated "bouts" of weightlessness, and this coincided with an increase in blood flow, especially in the arteries supplying the back of the brain. The blood-brain barrier opened, although there was no evidence of structural damage to the brain.
The researchers now plan to continue these studies with more detailed assessments of changes in blood and fluid in the brain, using imaging techniques like magnetic resonance imaging to confirm the results. They also want to consider introducing countermeasures like rubber pants, which create negative pressure in the lower body and help "pump" blood out of the astronaut's brain - and drugs that counteract the increase in nitric oxide. The results of such work could not only improve the well-being of astronauts in space travel, but also provide valuable information about why "gravity" is good for the brain.
Ilya Khel